TypeBuilder.DefineUninitializedData(String, Int32, FieldAttributes) 方法

public:
 System::Reflection::Emit::FieldBuilder ^ DefineUninitializedData(System::String ^ name, int size, System::Reflection::FieldAttributes attributes);

public System.Reflection.Emit.FieldBuilder DefineUninitializedData(string name, int size, System.Reflection.FieldAttributes attributes);

member this.DefineUninitializedData : string * int * System.Reflection.FieldAttributes -> System.Reflection.Emit.FieldBuilder

Public Function DefineUninitializedData (name As String, size As Integer, attributes As FieldAttributes) As FieldBuilder

参数

返回

用于引用数据的字段。

例外

示例

下面的代码示例演示如何使用 DefineUninitializedData 在动态类型中创建未初始化的数据字段：

using System;
using System.Threading;
using System.Reflection;
using System.Reflection.Emit;
using System.Runtime.InteropServices;
using System.Security.Permissions;

public sealed class Example
{
   public static void Main()
   {
      Type myHelloWorldType = CreateCallee(Thread.GetDomain());
      object myHelloWorldInstance =
      Activator.CreateInstance(myHelloWorldType);
      FieldInfo myGreetingFieldInfo =
      myHelloWorldType.GetField("MyGreeting");
      object oval = Activator.CreateInstance(myGreetingFieldInfo.FieldType);
      IntPtr myIntPtr = Marshal.AllocHGlobal(4);
      Random rand = new Random();
      int iTempSeed = rand.Next();
      byte[] bINITBYTE = GetRandBytes( iTempSeed, 4);
      IntPtr intptrTemp = myIntPtr;
      for ( int j = 0; j < 4; j++ )
      {
         Marshal.WriteByte( myIntPtr, bINITBYTE[j]);
         myIntPtr = (IntPtr)((int)myIntPtr + 1);
      }
      myIntPtr = intptrTemp;
      Object oValNew = Marshal.PtrToStructure( myIntPtr, myGreetingFieldInfo.FieldType);
      Marshal.FreeHGlobal( myIntPtr );

      myIntPtr = Marshal.AllocHGlobal(4);
      object myObj = myGreetingFieldInfo.GetValue(myHelloWorldInstance);
      Marshal.StructureToPtr(myObj, myIntPtr, true);
      intptrTemp = myIntPtr;
      Console.WriteLine("The value of 'MyGreeting' field : ");
      for ( int j = 0; j < 4; j++ )
      {
         Marshal.WriteByte( myIntPtr, bINITBYTE[j]);
         Console.WriteLine(bINITBYTE[j]);
         myIntPtr = (IntPtr)((int)myIntPtr + 1);
      }
   }

   private static byte[] GetRandBytes( int iRandSeed, int iSize )
   {
      byte[] barr = new byte[iSize];
      Random randTemp = new Random( iRandSeed );
      randTemp.NextBytes( barr );
      return barr;
   }

   // Create the callee transient dynamic assembly.
   private static Type CreateCallee(AppDomain myDomain)
   {
      // Create a simple name for the callee assembly.
      AssemblyName myAssemblyName = new AssemblyName();
      myAssemblyName.Name = "EmittedClass";

      // Create the callee dynamic assembly.
      AssemblyBuilder myAssembly =
         myDomain.DefineDynamicAssembly(myAssemblyName,AssemblyBuilderAccess.Run);

      // Create a dynamic module in the callee assembly.
      ModuleBuilder myModule =
         myAssembly.DefineDynamicModule("EmittedModule");

      // Define a public class named "MyHelloWorld"
      TypeBuilder myHelloWorldType =
         myModule.DefineType("MyHelloWorld", TypeAttributes.Public);

      // Define a 'MyGreeting' field and initialize it.
      FieldBuilder myFieldBuilder =
         myHelloWorldType.DefineUninitializedData("MyGreeting",4,FieldAttributes.Public);

      // Create the 'MyHelloWorld' class.
      return(myHelloWorldType.CreateType());
   }

   private Example() {}
}

Imports System.Threading
Imports System.Reflection
Imports System.Reflection.Emit
Imports System.Runtime.InteropServices


Module Example

   Sub Main()
      Dim myHelloWorldType As Type = CreateCallee(Thread.GetDomain())
      Dim myHelloWorldInstance As Object = Activator.CreateInstance(myHelloWorldType)
      Dim myGreetingFieldInfo As FieldInfo = myHelloWorldType.GetField("MyGreeting")
      Dim oval As Object = Activator.CreateInstance(myGreetingFieldInfo.FieldType)
      Dim myIntPtr As IntPtr = Marshal.AllocHGlobal(4)
      Dim rand As New Random()
      Dim iTempSeed As Integer = rand.Next()
      Dim bINITBYTE As Byte() = GetRandBytes(iTempSeed, 4)
      Dim intptrTemp As IntPtr = myIntPtr
      Dim j As Integer
      For j = 0 To 3
         Marshal.WriteByte(myIntPtr, bINITBYTE(j))
         myIntPtr = intptr.op_Explicit(myIntPtr.ToInt32 + 1)
      Next j
      myIntPtr = intptrTemp
      Dim oValNew As [Object] = Marshal.PtrToStructure(myIntPtr, myGreetingFieldInfo.FieldType)
      Marshal.FreeHGlobal(myIntPtr)

      myIntPtr = Marshal.AllocHGlobal(4)
      Dim myObj As Object = myGreetingFieldInfo.GetValue(myHelloWorldInstance)
      Marshal.StructureToPtr(myObj, myIntPtr, True)
      intptrTemp = myIntPtr
      Console.WriteLine("The value of 'MyGreeting' field : ")

      For j = 0 To 3
         Marshal.WriteByte(myIntPtr, bINITBYTE(j))
         Console.WriteLine(bINITBYTE(j))
         myIntPtr = intptr.op_Explicit(myIntPtr.ToInt32 + 1)
      Next j
   End Sub


   Private Function GetRandBytes(ByVal iRandSeed As Integer, ByVal iSize As Integer) As Byte()
      Dim barr(iSize) As Byte
      Dim randTemp As New Random(iRandSeed)
      randTemp.NextBytes(barr)
      Return barr
   End Function 'GetRandBytes


   ' Create the callee transient dynamic assembly.
   Private Function CreateCallee(ByVal myDomain As AppDomain) As Type
      ' Create a simple name for the callee assembly.
      Dim myAssemblyName As New AssemblyName()
      myAssemblyName.Name = "EmittedClass"

      ' Create the callee dynamic assembly.
      Dim myAssembly As AssemblyBuilder = myDomain.DefineDynamicAssembly(myAssemblyName, AssemblyBuilderAccess.Run)


      ' Create a dynamic module in the callee assembly.
      Dim myModule As ModuleBuilder = myAssembly.DefineDynamicModule("EmittedModule")

      ' Define a public class named "MyHelloWorld"
      Dim myHelloWorldType As TypeBuilder = myModule.DefineType("MyHelloWorld", TypeAttributes.Public)

      ' Define a 'MyGreeting' field and initialize it.
      Dim myFieldBuilder As FieldBuilder = myHelloWorldType.DefineUninitializedData("MyGreeting", 4, FieldAttributes.Public)

      ' Create the 'MyHelloWorld' class.
      Return myHelloWorldType.CreateType()
   End Function 'CreateCallee

End Module

注解

使用此方法创建的字段将为 static，即使参数中attributes不包含 FieldAttributes.Static 。