COM2IPerPropertyBrowsingHandler.cs source code in C# .NET

Source code for the .NET framework in C#

                        

Code:

/ 4.0 / 4.0 / DEVDIV_TFS / Dev10 / Releases / RTMRel / ndp / fx / src / WinForms / Managed / System / WinForms / ComponentModel / COM2Interop / COM2IPerPropertyBrowsingHandler.cs / 1305376 / COM2IPerPropertyBrowsingHandler.cs

                            //------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Windows.Forms.ComponentModel.Com2Interop { 
    using System.Runtime.Remoting; 
    using System.Runtime.InteropServices;
    using System.ComponentModel; 
    using System.Diagnostics;
    using System;
    using System.Collections;
    using Microsoft.Win32; 
    using System.Globalization;
    using System.Drawing.Design; 
 
    [System.Security.SuppressUnmanagedCodeSecurityAttribute()]
    internal class Com2IPerPropertyBrowsingHandler : Com2ExtendedBrowsingHandler { 
        public override Type Interface {
            get {
                return typeof(NativeMethods.IPerPropertyBrowsing);
            } 
        }
 
        public override void SetupPropertyHandlers(Com2PropertyDescriptor[] propDesc) { 
            if (propDesc == null) {
                return; 
            }
            for (int i = 0; i < propDesc.Length; i++) {
                propDesc[i].QueryGetBaseAttributes += new GetAttributesEventHandler(this.OnGetBaseAttributes);
                propDesc[i].QueryGetDisplayValue += new GetNameItemEventHandler(this.OnGetDisplayValue); 

                propDesc[i].QueryGetTypeConverterAndTypeEditor += new GetTypeConverterAndTypeEditorEventHandler(this.OnGetTypeConverterAndTypeEditor); 
            } 
        }
 
        private Guid GetPropertyPageGuid(NativeMethods.IPerPropertyBrowsing target, int dispid) {
            // check for a property page
            Guid guid;
            int hr = target.MapPropertyToPage(dispid, out guid); 
            if (hr == NativeMethods.S_OK) {
                return guid; 
            } 
            return Guid.Empty;
        } 

        internal static string GetDisplayString(NativeMethods.IPerPropertyBrowsing ppb, int dispid, ref bool success) {
            string[] strVal = new string[1];
            int hr = ppb.GetDisplayString(dispid, strVal); 
            if (hr == NativeMethods.S_OK) {
                success = (strVal[0] != null); 
                //Debug.Assert(success, "IPerPropertyBrowsing::GetDisplayString returned NULL and S_OK -- this is not a valid state. This component does not property implement IPerPropertyBrowsing. (component class=" + TypeDescriptor.GetClassName(ppb) + ")"); 
                return strVal[0];
            } 
            else {
                success = false;
            }
            return null; 
        }
 
        ///  
        /// 
        /// Here is where we handle IVsPerPropertyBrowsing.GetLocalizedPropertyInfo and IVsPerPropertyBrowsing.   HideProperty 
        /// such as IPerPropertyBrowsing, IProvidePropertyBuilder, etc.
        /// 
        private void OnGetBaseAttributes(Com2PropertyDescriptor sender, GetAttributesEvent attrEvent) {
            NativeMethods.IPerPropertyBrowsing target = sender.TargetObject as NativeMethods.IPerPropertyBrowsing; 
            if (target != null) {
                // we hide IDispatch props by default, we we need to force showing them here 
 
                bool validPropPage = !Guid.Empty.Equals(GetPropertyPageGuid(target, sender.DISPID));
 
                if (sender.CanShow && validPropPage) {
                    if (typeof(UnsafeNativeMethods.IDispatch).IsAssignableFrom(sender.PropertyType)) {
                        attrEvent.Add(BrowsableAttribute.Yes);
                    } 
                }
            } 
        } 

        private void OnGetDisplayValue(Com2PropertyDescriptor sender, GetNameItemEvent gnievent) { 
            try {
                if (sender.TargetObject is NativeMethods.IPerPropertyBrowsing) {

                    // if we are using the dropdown, don't convert the value 
                    // or the values will change when we select them and call back
                    // for the display value. 
                    if (sender.Converter is Com2IPerPropertyEnumConverter || sender.ConvertingNativeType) { 
                        return;
                    } 

                    bool success = true;

                    string displayString = GetDisplayString((NativeMethods.IPerPropertyBrowsing)sender.TargetObject, sender.DISPID, ref success); 

                    if (success) { 
                        gnievent.Name = displayString; 
                    }
                } 
            }
            catch {
            }
        } 

        private void OnGetTypeConverterAndTypeEditor(Com2PropertyDescriptor sender, GetTypeConverterAndTypeEditorEvent gveevent) { 
            if (sender.TargetObject is NativeMethods.IPerPropertyBrowsing) { 
                NativeMethods.IPerPropertyBrowsing ppb = (NativeMethods.IPerPropertyBrowsing)sender.TargetObject;
 
                bool hasStrings = false;

                // check for enums
                NativeMethods.CA_STRUCT caStrings = new NativeMethods.CA_STRUCT(); 
                NativeMethods.CA_STRUCT caCookies = new NativeMethods.CA_STRUCT();
 
                int hr = NativeMethods.S_OK; 

                try { 
                    hr = ppb.GetPredefinedStrings(sender.DISPID, caStrings, caCookies);
                }
                catch(ExternalException ex){
                    hr = ex.ErrorCode; 
                    Debug.Fail("An exception occurred inside IPerPropertyBrowsing::GetPredefinedStrings(dispid=" + sender.DISPID + "), object type=" + new ComNativeDescriptor().GetClassName(ppb) + ".  This is caused by an exception (usually an AV) inside the object being browsed, and is not a problem in the properties window.");
                } 
 
                // Terminate the existing editor if we created the current one
                // so if the items have disappeared, we don't hold onto the old 
                // items.
                if (gveevent.TypeConverter is Com2IPerPropertyEnumConverter) {
                    gveevent.TypeConverter = null;
                } 

                if (hr != NativeMethods.S_OK) { 
                    hasStrings = false; 
                }
                else { 
                    hasStrings = true;
                }

                if (hasStrings) { 

                    OleStrCAMarshaler stringMarshaler = new OleStrCAMarshaler(caStrings); 
                    Int32CAMarshaler  intMarshaler = new Int32CAMarshaler(caCookies); 

 
                    if (stringMarshaler.Count > 0 && intMarshaler.Count > 0) {
                        gveevent.TypeConverter = new Com2IPerPropertyEnumConverter(new Com2IPerPropertyBrowsingEnum(sender, this, stringMarshaler, intMarshaler, true));
                    }
                    else { 
                        //hasStrings = false;
                    } 
                } 

               // if we didn't get any strings, try the proppage edtior 
               //
               if (!hasStrings){

                 // this is a _bit_ of a backwards-compat work around... 
                 // many older ActiveX controls will show a property page
                 // for all properties since the old grid would only put up the 
                 // [...] button for "(Custom)".  If we have a conversion editor, 
                 // don't allow this to override it...
                 // 
                 if (sender.ConvertingNativeType){
                     return;
                 }
 
                 Guid g = GetPropertyPageGuid(ppb, sender.DISPID);
 
                 if (!Guid.Empty.Equals(g)){ 
                    gveevent.TypeEditor = new Com2PropertyPageUITypeEditor(sender, g, (UITypeEditor)gveevent.TypeEditor);
                 } 
               }
            }
        }
 

         // this is just here so we can identify the enums that we added 
         private class Com2IPerPropertyEnumConverter : Com2EnumConverter { 
             private Com2IPerPropertyBrowsingEnum itemsEnum;
             public Com2IPerPropertyEnumConverter(Com2IPerPropertyBrowsingEnum items) : base(items) { 
                this.itemsEnum = items;
             }

             public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destType) { 

                 if (destType == typeof(string) && !itemsEnum.arraysFetched) { 
                     object curValue = itemsEnum.target.GetValue(itemsEnum.target.TargetObject); 
                     if (curValue == value || (curValue != null && curValue.Equals(value))) {
                         bool success = false; 
                         string val = GetDisplayString((NativeMethods.IPerPropertyBrowsing)itemsEnum.target.TargetObject, itemsEnum.target.DISPID, ref success);
                         if (success) {
                             return val;
                         } 
                     }
                 } 
                 return base.ConvertTo(context, culture, value, destType); 
              }
         } 


         // This exists for perf reasons.   We delay doing this until we
         // are actually asked for the array of values. 
         //
         private class Com2IPerPropertyBrowsingEnum : Com2Enum { 
 
             internal Com2PropertyDescriptor target;
             private Com2IPerPropertyBrowsingHandler handler; 
             private OleStrCAMarshaler    nameMarshaller;
             private Int32CAMarshaler     valueMarshaller;
             internal bool                 arraysFetched;
             //private bool                 standardValuesQueried; 

             public Com2IPerPropertyBrowsingEnum(Com2PropertyDescriptor targetObject, Com2IPerPropertyBrowsingHandler handler, OleStrCAMarshaler names, Int32CAMarshaler values, bool allowUnknowns) : base(new string[0], new object[0], allowUnknowns) { 
                this.target = targetObject; 
                this.nameMarshaller = names;
                this.valueMarshaller = values; 
                this.handler = handler;
                this.arraysFetched = false;
             }
 
             /// 
             ///  
             /// Retrieve a copy of the value array 
             /// 
             public override object[] Values { 
                get {
                    EnsureArrays();
                    return base.Values;
                } 
             }
 
             ///  
             /// 
             /// Retrieve a copy of the nme array. 
             /// 
             public override string[] Names {
                get {
                    EnsureArrays(); 
                    return base.Names;
                } 
             } 

             /*internal bool StandardValuesQueried { 
                get {
                    this.standardValuesQueried = value;
                }
             } */ 

 
             // ensure that we have processed the caStructs into arrays 
             // of values and strings
             // 
             private void EnsureArrays() {
                if (this.arraysFetched) {
                    return;
                } 

                this.arraysFetched = true; 
 
                try {
                    // marshal the items. 
                    object[] nameItems = nameMarshaller.Items;
                    object[] cookieItems=   valueMarshaller.Items;

                    NativeMethods.IPerPropertyBrowsing ppb = (NativeMethods.IPerPropertyBrowsing)target.TargetObject; 
                    int itemCount = 0;
 
                    Debug.Assert(cookieItems != null && nameItems != null, "An item array is null"); 

 
                    if (nameItems.Length > 0){

                        object[] valueItems = new object[cookieItems.Length];
                        NativeMethods.VARIANT var = new NativeMethods.VARIANT(); 
                        int cookie;
 
                        Debug.Assert(cookieItems.Length == nameItems.Length, "Got uneven names and cookies"); 

                        // for each name item, we ask the object for it's corresponding value. 
                        //
                        Type targetType = target.PropertyType;
                        for (int i = nameItems.Length - 1; i >= 0; i--) {
                            cookie = (int)cookieItems[i]; 
                            if (nameItems[i] == null || !(nameItems[i] is string)) {
                                Debug.Fail("Bad IPerPropertyBrowsing item [" + i.ToString(CultureInfo.InvariantCulture) + "], name=" + (nameItems == null ? "(unknown)" : nameItems[i].ToString())); 
                                continue; 
                            }
                            var.vt = (short)NativeMethods.tagVT.VT_EMPTY; 
                            int hr = ppb.GetPredefinedValue(target.DISPID, cookie, var);
                            if (hr == NativeMethods.S_OK && var.vt != (short)NativeMethods.tagVT.VT_EMPTY) {
                                valueItems[i] = var.ToObject();
                                if (valueItems[i].GetType() != targetType) { 
                                    if (targetType.IsEnum) {
                                        valueItems[i] = Enum.ToObject(targetType, valueItems[i]); 
                                    } 
                                    else {
                                        try { 
                                            valueItems[i] = Convert.ChangeType(valueItems[i], targetType, CultureInfo.InvariantCulture);
                                        }
                                        catch {
                                            // oh well... 
                                        }
                                    } 
                                } 
                            }
 
                            var.Clear();
                            if (hr == NativeMethods.S_OK) {
                                itemCount++;
                                continue; 
                            }
                            else if (itemCount > 0){ 
                                // shorten the arrays to ignore the failed ones.  this isn't terribly 
                                // efficient but shouldn't happen very often.  It's rare for these to fail.
                                // 
                                Array.Copy(nameItems, i, nameItems, i+1, itemCount);
                                Array.Copy(valueItems, i, valueItems, i+1, itemCount);
                            }
 
                        }
 
                        // pass this data down to the base Com2Enum object... 
                        string[] strings = new string[itemCount];
                        Array.Copy(nameItems, 0, strings, 0, itemCount); 
                        base.PopulateArrays(strings, valueItems);

                    }
                } 
                catch (Exception ex) {
                    base.PopulateArrays(new string[0], new object[0]); 
                    Debug.Fail("Failed to build IPerPropertyBrowsing editor. " + ex.GetType().Name + ", " + ex.Message); 
                }
             } 

             protected override void PopulateArrays(string[] names, object[] values) {
                // we call base.PopulateArrays directly when we actually want to do this.
             } 

             public override object FromString(string s) { 
                EnsureArrays(); 
                return base.FromString(s);
             } 

             public override string ToString(object v) {

                // If the value is the object's current value, then 
                // ask GetDisplay string first.  This is a perf improvement
                // because this way we don't populate the arrays when an object is selected, only 
                // when the dropdown is actually opened. 
                //
                if (target.IsCurrentValue(v)) { 

                    bool success = false;

                    string displayString = Com2IPerPropertyBrowsingHandler.GetDisplayString((NativeMethods.IPerPropertyBrowsing)target.TargetObject, target.DISPID, ref success); 

                    if (success) { 
                        return displayString; 
                    }
                } 

                // couldn't get a display string...do the normal thing.
                //
                EnsureArrays(); 
                return base.ToString(v);
             } 
         } 

    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
//------------------------------------------------------------------------------ 
// 
//     Copyright (c) Microsoft Corporation.  All rights reserved.
// 
//----------------------------------------------------------------------------- 

namespace System.Windows.Forms.ComponentModel.Com2Interop { 
    using System.Runtime.Remoting; 
    using System.Runtime.InteropServices;
    using System.ComponentModel; 
    using System.Diagnostics;
    using System;
    using System.Collections;
    using Microsoft.Win32; 
    using System.Globalization;
    using System.Drawing.Design; 
 
    [System.Security.SuppressUnmanagedCodeSecurityAttribute()]
    internal class Com2IPerPropertyBrowsingHandler : Com2ExtendedBrowsingHandler { 
        public override Type Interface {
            get {
                return typeof(NativeMethods.IPerPropertyBrowsing);
            } 
        }
 
        public override void SetupPropertyHandlers(Com2PropertyDescriptor[] propDesc) { 
            if (propDesc == null) {
                return; 
            }
            for (int i = 0; i < propDesc.Length; i++) {
                propDesc[i].QueryGetBaseAttributes += new GetAttributesEventHandler(this.OnGetBaseAttributes);
                propDesc[i].QueryGetDisplayValue += new GetNameItemEventHandler(this.OnGetDisplayValue); 

                propDesc[i].QueryGetTypeConverterAndTypeEditor += new GetTypeConverterAndTypeEditorEventHandler(this.OnGetTypeConverterAndTypeEditor); 
            } 
        }
 
        private Guid GetPropertyPageGuid(NativeMethods.IPerPropertyBrowsing target, int dispid) {
            // check for a property page
            Guid guid;
            int hr = target.MapPropertyToPage(dispid, out guid); 
            if (hr == NativeMethods.S_OK) {
                return guid; 
            } 
            return Guid.Empty;
        } 

        internal static string GetDisplayString(NativeMethods.IPerPropertyBrowsing ppb, int dispid, ref bool success) {
            string[] strVal = new string[1];
            int hr = ppb.GetDisplayString(dispid, strVal); 
            if (hr == NativeMethods.S_OK) {
                success = (strVal[0] != null); 
                //Debug.Assert(success, "IPerPropertyBrowsing::GetDisplayString returned NULL and S_OK -- this is not a valid state. This component does not property implement IPerPropertyBrowsing. (component class=" + TypeDescriptor.GetClassName(ppb) + ")"); 
                return strVal[0];
            } 
            else {
                success = false;
            }
            return null; 
        }
 
        ///  
        /// 
        /// Here is where we handle IVsPerPropertyBrowsing.GetLocalizedPropertyInfo and IVsPerPropertyBrowsing.   HideProperty 
        /// such as IPerPropertyBrowsing, IProvidePropertyBuilder, etc.
        /// 
        private void OnGetBaseAttributes(Com2PropertyDescriptor sender, GetAttributesEvent attrEvent) {
            NativeMethods.IPerPropertyBrowsing target = sender.TargetObject as NativeMethods.IPerPropertyBrowsing; 
            if (target != null) {
                // we hide IDispatch props by default, we we need to force showing them here 
 
                bool validPropPage = !Guid.Empty.Equals(GetPropertyPageGuid(target, sender.DISPID));
 
                if (sender.CanShow && validPropPage) {
                    if (typeof(UnsafeNativeMethods.IDispatch).IsAssignableFrom(sender.PropertyType)) {
                        attrEvent.Add(BrowsableAttribute.Yes);
                    } 
                }
            } 
        } 

        private void OnGetDisplayValue(Com2PropertyDescriptor sender, GetNameItemEvent gnievent) { 
            try {
                if (sender.TargetObject is NativeMethods.IPerPropertyBrowsing) {

                    // if we are using the dropdown, don't convert the value 
                    // or the values will change when we select them and call back
                    // for the display value. 
                    if (sender.Converter is Com2IPerPropertyEnumConverter || sender.ConvertingNativeType) { 
                        return;
                    } 

                    bool success = true;

                    string displayString = GetDisplayString((NativeMethods.IPerPropertyBrowsing)sender.TargetObject, sender.DISPID, ref success); 

                    if (success) { 
                        gnievent.Name = displayString; 
                    }
                } 
            }
            catch {
            }
        } 

        private void OnGetTypeConverterAndTypeEditor(Com2PropertyDescriptor sender, GetTypeConverterAndTypeEditorEvent gveevent) { 
            if (sender.TargetObject is NativeMethods.IPerPropertyBrowsing) { 
                NativeMethods.IPerPropertyBrowsing ppb = (NativeMethods.IPerPropertyBrowsing)sender.TargetObject;
 
                bool hasStrings = false;

                // check for enums
                NativeMethods.CA_STRUCT caStrings = new NativeMethods.CA_STRUCT(); 
                NativeMethods.CA_STRUCT caCookies = new NativeMethods.CA_STRUCT();
 
                int hr = NativeMethods.S_OK; 

                try { 
                    hr = ppb.GetPredefinedStrings(sender.DISPID, caStrings, caCookies);
                }
                catch(ExternalException ex){
                    hr = ex.ErrorCode; 
                    Debug.Fail("An exception occurred inside IPerPropertyBrowsing::GetPredefinedStrings(dispid=" + sender.DISPID + "), object type=" + new ComNativeDescriptor().GetClassName(ppb) + ".  This is caused by an exception (usually an AV) inside the object being browsed, and is not a problem in the properties window.");
                } 
 
                // Terminate the existing editor if we created the current one
                // so if the items have disappeared, we don't hold onto the old 
                // items.
                if (gveevent.TypeConverter is Com2IPerPropertyEnumConverter) {
                    gveevent.TypeConverter = null;
                } 

                if (hr != NativeMethods.S_OK) { 
                    hasStrings = false; 
                }
                else { 
                    hasStrings = true;
                }

                if (hasStrings) { 

                    OleStrCAMarshaler stringMarshaler = new OleStrCAMarshaler(caStrings); 
                    Int32CAMarshaler  intMarshaler = new Int32CAMarshaler(caCookies); 

 
                    if (stringMarshaler.Count > 0 && intMarshaler.Count > 0) {
                        gveevent.TypeConverter = new Com2IPerPropertyEnumConverter(new Com2IPerPropertyBrowsingEnum(sender, this, stringMarshaler, intMarshaler, true));
                    }
                    else { 
                        //hasStrings = false;
                    } 
                } 

               // if we didn't get any strings, try the proppage edtior 
               //
               if (!hasStrings){

                 // this is a _bit_ of a backwards-compat work around... 
                 // many older ActiveX controls will show a property page
                 // for all properties since the old grid would only put up the 
                 // [...] button for "(Custom)".  If we have a conversion editor, 
                 // don't allow this to override it...
                 // 
                 if (sender.ConvertingNativeType){
                     return;
                 }
 
                 Guid g = GetPropertyPageGuid(ppb, sender.DISPID);
 
                 if (!Guid.Empty.Equals(g)){ 
                    gveevent.TypeEditor = new Com2PropertyPageUITypeEditor(sender, g, (UITypeEditor)gveevent.TypeEditor);
                 } 
               }
            }
        }
 

         // this is just here so we can identify the enums that we added 
         private class Com2IPerPropertyEnumConverter : Com2EnumConverter { 
             private Com2IPerPropertyBrowsingEnum itemsEnum;
             public Com2IPerPropertyEnumConverter(Com2IPerPropertyBrowsingEnum items) : base(items) { 
                this.itemsEnum = items;
             }

             public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destType) { 

                 if (destType == typeof(string) && !itemsEnum.arraysFetched) { 
                     object curValue = itemsEnum.target.GetValue(itemsEnum.target.TargetObject); 
                     if (curValue == value || (curValue != null && curValue.Equals(value))) {
                         bool success = false; 
                         string val = GetDisplayString((NativeMethods.IPerPropertyBrowsing)itemsEnum.target.TargetObject, itemsEnum.target.DISPID, ref success);
                         if (success) {
                             return val;
                         } 
                     }
                 } 
                 return base.ConvertTo(context, culture, value, destType); 
              }
         } 


         // This exists for perf reasons.   We delay doing this until we
         // are actually asked for the array of values. 
         //
         private class Com2IPerPropertyBrowsingEnum : Com2Enum { 
 
             internal Com2PropertyDescriptor target;
             private Com2IPerPropertyBrowsingHandler handler; 
             private OleStrCAMarshaler    nameMarshaller;
             private Int32CAMarshaler     valueMarshaller;
             internal bool                 arraysFetched;
             //private bool                 standardValuesQueried; 

             public Com2IPerPropertyBrowsingEnum(Com2PropertyDescriptor targetObject, Com2IPerPropertyBrowsingHandler handler, OleStrCAMarshaler names, Int32CAMarshaler values, bool allowUnknowns) : base(new string[0], new object[0], allowUnknowns) { 
                this.target = targetObject; 
                this.nameMarshaller = names;
                this.valueMarshaller = values; 
                this.handler = handler;
                this.arraysFetched = false;
             }
 
             /// 
             ///  
             /// Retrieve a copy of the value array 
             /// 
             public override object[] Values { 
                get {
                    EnsureArrays();
                    return base.Values;
                } 
             }
 
             ///  
             /// 
             /// Retrieve a copy of the nme array. 
             /// 
             public override string[] Names {
                get {
                    EnsureArrays(); 
                    return base.Names;
                } 
             } 

             /*internal bool StandardValuesQueried { 
                get {
                    this.standardValuesQueried = value;
                }
             } */ 

 
             // ensure that we have processed the caStructs into arrays 
             // of values and strings
             // 
             private void EnsureArrays() {
                if (this.arraysFetched) {
                    return;
                } 

                this.arraysFetched = true; 
 
                try {
                    // marshal the items. 
                    object[] nameItems = nameMarshaller.Items;
                    object[] cookieItems=   valueMarshaller.Items;

                    NativeMethods.IPerPropertyBrowsing ppb = (NativeMethods.IPerPropertyBrowsing)target.TargetObject; 
                    int itemCount = 0;
 
                    Debug.Assert(cookieItems != null && nameItems != null, "An item array is null"); 

 
                    if (nameItems.Length > 0){

                        object[] valueItems = new object[cookieItems.Length];
                        NativeMethods.VARIANT var = new NativeMethods.VARIANT(); 
                        int cookie;
 
                        Debug.Assert(cookieItems.Length == nameItems.Length, "Got uneven names and cookies"); 

                        // for each name item, we ask the object for it's corresponding value. 
                        //
                        Type targetType = target.PropertyType;
                        for (int i = nameItems.Length - 1; i >= 0; i--) {
                            cookie = (int)cookieItems[i]; 
                            if (nameItems[i] == null || !(nameItems[i] is string)) {
                                Debug.Fail("Bad IPerPropertyBrowsing item [" + i.ToString(CultureInfo.InvariantCulture) + "], name=" + (nameItems == null ? "(unknown)" : nameItems[i].ToString())); 
                                continue; 
                            }
                            var.vt = (short)NativeMethods.tagVT.VT_EMPTY; 
                            int hr = ppb.GetPredefinedValue(target.DISPID, cookie, var);
                            if (hr == NativeMethods.S_OK && var.vt != (short)NativeMethods.tagVT.VT_EMPTY) {
                                valueItems[i] = var.ToObject();
                                if (valueItems[i].GetType() != targetType) { 
                                    if (targetType.IsEnum) {
                                        valueItems[i] = Enum.ToObject(targetType, valueItems[i]); 
                                    } 
                                    else {
                                        try { 
                                            valueItems[i] = Convert.ChangeType(valueItems[i], targetType, CultureInfo.InvariantCulture);
                                        }
                                        catch {
                                            // oh well... 
                                        }
                                    } 
                                } 
                            }
 
                            var.Clear();
                            if (hr == NativeMethods.S_OK) {
                                itemCount++;
                                continue; 
                            }
                            else if (itemCount > 0){ 
                                // shorten the arrays to ignore the failed ones.  this isn't terribly 
                                // efficient but shouldn't happen very often.  It's rare for these to fail.
                                // 
                                Array.Copy(nameItems, i, nameItems, i+1, itemCount);
                                Array.Copy(valueItems, i, valueItems, i+1, itemCount);
                            }
 
                        }
 
                        // pass this data down to the base Com2Enum object... 
                        string[] strings = new string[itemCount];
                        Array.Copy(nameItems, 0, strings, 0, itemCount); 
                        base.PopulateArrays(strings, valueItems);

                    }
                } 
                catch (Exception ex) {
                    base.PopulateArrays(new string[0], new object[0]); 
                    Debug.Fail("Failed to build IPerPropertyBrowsing editor. " + ex.GetType().Name + ", " + ex.Message); 
                }
             } 

             protected override void PopulateArrays(string[] names, object[] values) {
                // we call base.PopulateArrays directly when we actually want to do this.
             } 

             public override object FromString(string s) { 
                EnsureArrays(); 
                return base.FromString(s);
             } 

             public override string ToString(object v) {

                // If the value is the object's current value, then 
                // ask GetDisplay string first.  This is a perf improvement
                // because this way we don't populate the arrays when an object is selected, only 
                // when the dropdown is actually opened. 
                //
                if (target.IsCurrentValue(v)) { 

                    bool success = false;

                    string displayString = Com2IPerPropertyBrowsingHandler.GetDisplayString((NativeMethods.IPerPropertyBrowsing)target.TargetObject, target.DISPID, ref success); 

                    if (success) { 
                        return displayString; 
                    }
                } 

                // couldn't get a display string...do the normal thing.
                //
                EnsureArrays(); 
                return base.ToString(v);
             } 
         } 

    } 
}

// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
                        

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