Condition.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / UIAutomation / UIAutomationClient / System / Windows / Automation / Condition.cs / 1305600 / Condition.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// 
// Description: 
//
// History: 
//  10/14/2003 : BrendanM - Created
//
//---------------------------------------------------------------------------
 
// PRESHARP: In order to avoid generating warnings about unkown message numbers and unknown pragmas.
#pragma warning disable 1634, 1691 
 
using System;
using MS.Internal.Automation; 
using System.Windows.Automation;
using System.Runtime.InteropServices;
using System.Runtime.CompilerServices;
 
namespace System.Windows.Automation
{ 
    // Internal Class that wraps the IntPtr to the Node 
    internal sealed class SafeConditionMemoryHandle : SafeHandle
    { 
        // Called by P/Invoke when returning SafeHandles
        // (Also used by UiaCoreApi to create invalid handles.)
        internal SafeConditionMemoryHandle()
            : base(IntPtr.Zero, true) 
        {
        } 
 
        // No need to provide a finalizer - SafeHandle's critical finalizer will
        // call ReleaseHandle for you. 
        public override bool IsInvalid
        {
            get { return handle == IntPtr.Zero; }
        } 

        override protected bool ReleaseHandle() 
        { 
            Marshal.FreeCoTaskMem(handle);
            return true; 
        }

        // uiaCondition is one of the Uia condition structs - eg UiaCoreApi.UiaAndOrCondition
        internal static SafeConditionMemoryHandle AllocateConditionHandle(object uiaCondition) 
        {
            // Allocate SafeHandle first to avoid failure later. 
            SafeConditionMemoryHandle sh = new SafeConditionMemoryHandle(); 
            int size = Marshal.SizeOf(uiaCondition);
 
            RuntimeHelpers.PrepareConstrainedRegions(); // ensures that the following finally block is atomic
            try { }
            finally
            { 
                IntPtr mem = Marshal.AllocCoTaskMem(size);
                sh.SetHandle(mem); 
            } 
            Marshal.StructureToPtr(uiaCondition, sh.handle, false);
            return sh; 
        }


        // used by And/Or conditions to allocate an array of pointers to other conditions 
        internal static SafeConditionMemoryHandle AllocateConditionArrayHandle(Condition [] conditions)
        { 
            // Allocate SafeHandle first to avoid failure later. 
            SafeConditionMemoryHandle sh = new SafeConditionMemoryHandle();
 
            int intPtrSize = Marshal.SizeOf(typeof(IntPtr));

            RuntimeHelpers.PrepareConstrainedRegions(); // ensures that the following finally block is atomic
            try { } 
            finally
            { 
                IntPtr mem = Marshal.AllocCoTaskMem(conditions.Length * intPtrSize); 
                sh.SetHandle(mem);
            } 

            unsafe
            // Suppress "Exposing unsafe code thru public interface" UiaCoreApi is trusted
#pragma warning suppress 56505 
            {
                IntPtr* pdata = (IntPtr*)sh.handle; 
                for (int i = 0; i < conditions.Length; i++) 
                {
                    *pdata++ = conditions[i]._safeHandle.handle; 
                }
            }
            return sh;
        } 

        // Can't pass null into an API that takes a SafeHandle - so using this instead... 
        internal static SafeConditionMemoryHandle NullHandle = new SafeConditionMemoryHandle(); 
    }
 



 
    /// 
    /// Base type for conditions used by LogicalElementSearcher. 
    ///  
#if (INTERNAL_COMPILE)
    internal abstract class Condition 
#else
    public abstract class Condition
#endif
    { 
        //-----------------------------------------------------
        // 
        //  Constructors 
        //
        //----------------------------------------------------- 

        #region Constructors

        // Internal ctor to prevent others from deriving from this class 
        internal Condition()
        { 
        } 

        #endregion Constructors 

        //------------------------------------------------------
        //
        //  Public readonly fields & constants 
        //
        //----------------------------------------------------- 
 
        #region Public readonly fields & constants
 
        /// Condition object that always evaluates to true
        public static readonly Condition TrueCondition = new BoolCondition(true);
        /// Condition object that always evaluates to false
        public static readonly Condition FalseCondition = new BoolCondition(false); 

        #endregion Public readonly fields & constants 
 
        //------------------------------------------------------
        // 
        //  Internal Methods
        //
        //------------------------------------------------------
 
        #region Internal Methods
 
        internal void SetMarshalData(object uiaCondition) 
        {
            // Takes one of the interop UiaCondition classes (from UiaCoreApi.cs), and allocs 
            // a SafeHandle with associated unmanaged memory - can then pass that to the UIA APIs.
            _safeHandle = SafeConditionMemoryHandle.AllocateConditionHandle(uiaCondition);
        }
 
        #endregion Internal Methods
 
        //----------------------------------------------------- 
        //
        //  Internal Fields 
        //
        //------------------------------------------------------

        #region Internal Fields 

        internal SafeConditionMemoryHandle _safeHandle; 
 
        #endregion Internal Fields
 

        //-----------------------------------------------------
        //
        //  Nested Classes 
        //
        //----------------------------------------------------- 
        private class BoolCondition: Condition 
        {
            internal BoolCondition(bool b) 
            {
                SetMarshalData(new UiaCoreApi.UiaCondition(b ? UiaCoreApi.ConditionType.True : UiaCoreApi.ConditionType.False));
            }
        } 
    }
} 

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