ControlParameter.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / fx / src / xsp / System / Web / UI / WebControls / ControlParameter.cs / 1 / ControlParameter.cs
                        

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

namespace System.Web.UI.WebControls { 
 
    using System;
    using System.ComponentModel; 
    using System.Web.UI.WebControls;
    using System.Security.Permissions;

 

    ///  
    /// Represents a Parameter that gets its value from a control's property. 
    /// 
    [ 
    DefaultProperty("ControlID"),
    ]
    [AspNetHostingPermission(SecurityAction.LinkDemand, Level=AspNetHostingPermissionLevel.Minimal)]
    [AspNetHostingPermission(SecurityAction.InheritanceDemand, Level=AspNetHostingPermissionLevel.Minimal)] 
    public class ControlParameter : Parameter {
 
 
        /// 
        /// Creates an instance of the ControlParameter class. 
        /// 
        public ControlParameter() {
        }
 

        ///  
        /// Creates an instance of the ControlParameter class with the specified parameter name and control ID. 
        /// 
        public ControlParameter(string name, string controlID) : base(name) { 
            ControlID = controlID;
        }

 
        /// 
        /// Creates an instance of the ControlParameter class with the specified parameter name, control ID, and property name. 
        ///  
        public ControlParameter(string name, string controlID, string propertyName) : base(name) {
            ControlID = controlID; 
            PropertyName = propertyName;
        }

 
        /// 
        /// Creates an instance of the ControlParameter class with the specified parameter name, type, control ID, and property name. 
        ///  
        public ControlParameter(string name, TypeCode type, string controlID, string propertyName) : base(name, type) {
            ControlID = controlID; 
            PropertyName = propertyName;
        }

 
        /// 
        /// Used to clone a parameter. 
        ///  
        protected ControlParameter(ControlParameter original) : base(original) {
            ControlID = original.ControlID; 
            PropertyName = original.PropertyName;
        }

 

        ///  
        /// The ID of the control to get the value from. 
        /// 
        [ 
        DefaultValue(""),
        IDReferenceProperty(),
        RefreshProperties(RefreshProperties.All),
        TypeConverter(typeof(ControlIDConverter)), 
        WebCategory("Control"),
        WebSysDescription(SR.ControlParameter_ControlID), 
        ] 
        public string ControlID {
            get { 
                object o = ViewState["ControlID"];
                if (o == null)
                    return String.Empty;
                return (string)o; 
            }
            set { 
                if (ControlID != value) { 
                    ViewState["ControlID"] = value;
                    OnParameterChanged(); 
                }
            }
        }
 

        ///  
        /// The name of the control's property to get the value from. 
        /// If none is specified, the ControlValueProperty attribute of the control will be examined to determine the default property name.
        ///  
        [
        DefaultValue(""),
        TypeConverter(typeof(ControlPropertyNameConverter)),
        WebCategory("Control"), 
        WebSysDescription(SR.ControlParameter_PropertyName),
        ] 
        public string PropertyName { 
            get {
                object o = ViewState["PropertyName"]; 
                if (o == null)
                    return String.Empty;
                return (string)o;
            } 
            set {
                if (PropertyName != value) { 
                    ViewState["PropertyName"] = value; 
                    OnParameterChanged();
                } 
            }
        }

 

        ///  
        /// Creates a new ControlParameter that is a copy of this ControlParameter. 
        /// 
        protected override Parameter Clone() { 
            return new ControlParameter(this);
        }

 
        /// 
        /// Returns the updated value of the parameter. 
        ///  
        protected override object Evaluate(HttpContext context, Control control) {
            if (control == null) { 
                return null;
            }

            string controlID = ControlID; 
            string propertyName = PropertyName;
 
            if (controlID.Length == 0) { 
                throw new ArgumentException(SR.GetString(SR.ControlParameter_ControlIDNotSpecified, Name));
            } 

            Control foundControl = DataBoundControlHelper.FindControl(control, controlID);

            if (foundControl == null) { 
                throw new InvalidOperationException(SR.GetString(SR.ControlParameter_CouldNotFindControl, controlID, Name));
            } 
 
            ControlValuePropertyAttribute controlValueProp = (ControlValuePropertyAttribute)TypeDescriptor.GetAttributes(foundControl)[typeof(ControlValuePropertyAttribute)];
 
            // If no property name is specified, use the ControlValuePropertyAttribute to determine which property to use.
            if (propertyName.Length == 0) {
                if ((controlValueProp != null) && (!String.IsNullOrEmpty(controlValueProp.Name))) {
                    propertyName = controlValueProp.Name; 
                }
                else { 
                    throw new InvalidOperationException(SR.GetString(SR.ControlParameter_PropertyNameNotSpecified, controlID, Name)); 
                }
            } 

            // Get the value of the property
            object value = DataBinder.Eval(foundControl, propertyName);
 
            // Convert the value to null if this is the default property and the value is the property's default value
            if (controlValueProp != null && 
                String.Equals(controlValueProp.Name, propertyName, StringComparison.OrdinalIgnoreCase) && 
                controlValueProp.DefaultValue != null &&
                controlValueProp.DefaultValue.Equals(value)) { 
                return null;
            }
            return value;
        } 
    }
}

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