TypeBuilder.GetField 方法
定義
重要
部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。
傳回目前 TypeBuilder 所定義的欄位。
多載
| GetField(Type, FieldInfo) |
傳回對應至泛型類型定義指定欄位的指定建構泛型類型的欄位。 |
| GetField(String, BindingFlags) |
傳回指定之名稱所指定的欄位。 |
GetField(Type, FieldInfo)
傳回對應至泛型類型定義指定欄位的指定建構泛型類型的欄位。
public:
static System::Reflection::FieldInfo ^ GetField(Type ^ type, System::Reflection::FieldInfo ^ field);public static System.Reflection.FieldInfo GetField (Type type, System.Reflection.FieldInfo field);static member GetField : Type * System.Reflection.FieldInfo -> System.Reflection.FieldInfoPublic Shared Function GetField (type As Type, field As FieldInfo) As FieldInfo參數
- type
- Type
傳回欄位的建構泛型類別。
- field
- FieldInfo
有關 type 的泛型類型定義欄位，指定要傳回的 type 欄位。
傳回
代表對應 field (其指定屬於 type 泛型類型定義的欄位) 的 type 欄位的 FieldInfo 物件。
例外狀況
範例
下列程式代碼範例包含名為 Sample 的泛型類別原始碼，其類型參數名為 T。 類別具有名為 Field的欄位，其類型 T為 ，以及名為的泛型方法 GM ， U其具有名為 的專屬型別參數。 方法GM會建立的Sample實例，將自己的型別參數取代為的型別參數USample，並將其輸入參數儲存在 中Field。 此原始碼已編譯但未使用;您可以使用 Ildasm.exe (IL 反組譯程式) 來檢視它，並將其與 類別 Example發出的程式代碼進行比較。
類別 Example 中的程式代碼示範如何使用 GetField 方法來發出泛型程序代碼。 類別Main的 方法會建立包含名為 Sample的類別的動態元件，並使用 DefineGenericParameters 方法，藉由新增名為T的Example型別參數來使其泛型。 無參數建構函式和類型 T為Field的欄位會新增至 類別Sample。 方法 GM 會使用 MethodBuilder.DefineGenericParameters 方法新增並轉換成泛型方法。 的 GM 型別參數名為 U。 定義型別參數之後，會使用 MethodBuilder.SetSignature 方法新增 的GM簽章。 沒有傳回型別和不需要或自定義修飾詞，因此此方法的所有參數除外nullparameterTypes;parameterTypes請將方法的唯一參數類型設定為 U，方法的泛型型別參數。 方法的主體會在 Visual Basic) 中建立建構型 Sample<U> 別 (Sample(Of U) 的實例、將方法的參數指派給 Field，然後列印 的值 Field。 方法GetField可用來建立 ，FieldInfo代表和 OpCodes.Ldfld 指令中OpCodes.Stfld建構泛型型別Sample<U>的欄位。
已定義虛擬類型來儲存進入點方法 Main。 在 的 Main主體中，靜態 GM 方法會在 Visual Basic) 中建構的泛型類型 Sample<int> (上叫 Sample(Of Integer) 用，型 String 別取代為 U。
執行程式代碼範例時，它會將發出的元件儲存為 TypeBuilderGetFieldExample.exe。 您可以執行 TypeBuilderGetFieldExample.exe，而且您可以使用 Ildasm.exe (IL 反組譯程式) 來比較發出的程式代碼與編譯成程式代碼範例本身之類別的程式代碼 Sample 。
using System;
using System.Reflection;
using System.Reflection.Emit;
// Compare the MSIL in this class to the MSIL
// generated by the Reflection.Emit code in class
// Example.
public class Sample<T>
{
public T Field;
public static void GM<U>(U val)
{
Sample<U> s = new Sample<U>();
s.Field = val;
Console.WriteLine(s.Field);
}
}
public class Example
{
public static void Main()
{
AppDomain myDomain = AppDomain.CurrentDomain;
AssemblyName myAsmName =
new AssemblyName("TypeBuilderGetFieldExample");
AssemblyBuilder myAssembly = myDomain.DefineDynamicAssembly(
myAsmName, AssemblyBuilderAccess.Save);
ModuleBuilder myModule = myAssembly.DefineDynamicModule(
myAsmName.Name,
myAsmName.Name + ".exe");
// Define the sample type.
TypeBuilder myType = myModule.DefineType("Sample",
TypeAttributes.Class | TypeAttributes.Public);
// Add a type parameter, making the type generic.
string[] typeParamNames = {"T"};
GenericTypeParameterBuilder[] typeParams =
myType.DefineGenericParameters(typeParamNames);
// Define a default constructor. Normally it would
// not be necessary to define the default constructor,
// but in this case it is needed for the call to
// TypeBuilder.GetConstructor, which gets the default
// constructor for the generic type constructed from
// Sample<T>, in the generic method GM<U>.
ConstructorBuilder ctor = myType.DefineDefaultConstructor(
MethodAttributes.PrivateScope | MethodAttributes.Public |
MethodAttributes.HideBySig | MethodAttributes.SpecialName |
MethodAttributes.RTSpecialName);
// Add a field of type T, with the name Field.
FieldBuilder myField = myType.DefineField("Field",
typeParams[0],
FieldAttributes.Public);
// Add a method and make it generic, with a type
// parameter named U. Note how similar this is to
// the way Sample is turned into a generic type. The
// method has no signature, because the type of its
// only parameter is U, which is not yet defined.
MethodBuilder genMethod = myType.DefineMethod("GM",
MethodAttributes.Public | MethodAttributes.Static);
string[] methodParamNames = {"U"};
GenericTypeParameterBuilder[] methodParams =
genMethod.DefineGenericParameters(methodParamNames);
// Now add a signature for genMethod, specifying U
// as the type of the parameter. There is no return value
// and no custom modifiers.
genMethod.SetSignature(null, null, null,
new Type[] { methodParams[0] }, null, null);
// Emit a method body for the generic method.
ILGenerator ilg = genMethod.GetILGenerator();
// Construct the type Sample<U> using MakeGenericType.
Type SampleOfU = myType.MakeGenericType( methodParams[0] );
// Create a local variable to store the instance of
// Sample<U>.
ilg.DeclareLocal(SampleOfU);
// Call the default constructor. Note that it is
// necessary to have the default constructor for the
// constructed generic type Sample<U>; use the
// TypeBuilder.GetConstructor method to obtain this
// constructor.
ConstructorInfo ctorOfU = TypeBuilder.GetConstructor(
SampleOfU, ctor);
ilg.Emit(OpCodes.Newobj, ctorOfU);
// Store the instance in the local variable; load it
// again, and load the parameter of genMethod.
ilg.Emit(OpCodes.Stloc_0);
ilg.Emit(OpCodes.Ldloc_0);
ilg.Emit(OpCodes.Ldarg_0);
// In order to store the value in the field of the
// instance of Sample<U>, it is necessary to have
// a FieldInfo representing the field of the
// constructed type. Use TypeBuilder.GetField to
// obtain this FieldInfo.
FieldInfo FieldOfU = TypeBuilder.GetField(
SampleOfU, myField);
// Store the value in the field.
ilg.Emit(OpCodes.Stfld, FieldOfU);
// Load the instance, load the field value, box it
// (specifying the type of the type parameter, U), and
// print it.
ilg.Emit(OpCodes.Ldloc_0);
ilg.Emit(OpCodes.Ldfld, FieldOfU);
ilg.Emit(OpCodes.Box, methodParams[0]);
MethodInfo writeLineObj =
typeof(Console).GetMethod("WriteLine",
new Type[] { typeof(object) });
ilg.EmitCall(OpCodes.Call, writeLineObj, null);
ilg.Emit(OpCodes.Ret);
// Emit an entry point method; this must be in a
// non-generic type.
TypeBuilder dummy = myModule.DefineType("Dummy",
TypeAttributes.Class | TypeAttributes.NotPublic);
MethodBuilder entryPoint = dummy.DefineMethod("Main",
MethodAttributes.Public | MethodAttributes.Static,
null, null);
ilg = entryPoint.GetILGenerator();
// In order to call the static generic method GM, it is
// necessary to create a constructed type from the
// generic type definition for Sample. This can be any
// constructed type; in this case Sample<int> is used.
Type SampleOfInt =
myType.MakeGenericType( typeof(int) );
// Next get a MethodInfo representing the static generic
// method GM on type Sample<int>.
MethodInfo SampleOfIntGM = TypeBuilder.GetMethod(SampleOfInt,
genMethod);
// Next get a MethodInfo for GM<string>, which is the
// instantiation of GM that Main calls.
MethodInfo GMOfString =
SampleOfIntGM.MakeGenericMethod( typeof(string) );
// Finally, emit the call. Push a string onto
// the stack, as the argument for the generic method.
ilg.Emit(OpCodes.Ldstr, "Hello, world!");
ilg.EmitCall(OpCodes.Call, GMOfString, null);
ilg.Emit(OpCodes.Ret);
myType.CreateType();
dummy.CreateType();
myAssembly.SetEntryPoint(entryPoint);
myAssembly.Save(myAsmName.Name + ".exe");
Console.WriteLine(myAsmName.Name + ".exe has been saved.");
}
}
Imports System.Reflection
Imports System.Reflection.Emit
' Compare the MSIL in this class to the MSIL
' generated by the Reflection.Emit code in class
' Example.
Public Class Sample(Of T)
Public Field As T
Public Shared Sub GM(Of U)(ByVal val As U)
Dim s As New Sample(Of U)
s.Field = val
Console.WriteLine(s.Field)
End Sub
End Class
Public Class Example
Public Shared Sub Main()
Dim myDomain As AppDomain = AppDomain.CurrentDomain
Dim myAsmName As New AssemblyName("TypeBuilderGetFieldExample")
Dim myAssembly As AssemblyBuilder = _
myDomain.DefineDynamicAssembly(myAsmName, _
AssemblyBuilderAccess.Save)
Dim myModule As ModuleBuilder = _
myAssembly.DefineDynamicModule(myAsmName.Name, _
myAsmName.Name & ".exe")
' Define the sample type.
Dim myType As TypeBuilder = myModule.DefineType( _
"Sample", _
TypeAttributes.Class Or TypeAttributes.Public)
' Add a type parameter, making the type generic.
Dim typeParamNames() As String = { "T" }
Dim typeParams As GenericTypeParameterBuilder() = _
myType.DefineGenericParameters(typeParamNames)
' Define a default constructor. Normally it would
' not be necessary to define the default constructor,
' but in this case it is needed for the call to
' TypeBuilder.GetConstructor, which gets the default
' constructor for the generic type constructed from
' Sample(Of T), in the generic method GM(Of U).
Dim ctor As ConstructorBuilder = _
myType.DefineDefaultConstructor( _
MethodAttributes.PrivateScope Or MethodAttributes.Public _
Or MethodAttributes.HideBySig Or MethodAttributes.SpecialName _
Or MethodAttributes.RTSpecialName)
' Add a field of type T, with the name Field.
Dim myField As FieldBuilder = myType.DefineField( _
"Field", typeParams(0), FieldAttributes.Public)
' Add a method and make it generic, with a type
' parameter named U. Note how similar this is to
' the way Sample is turned into a generic type. The
' method has no signature, because the type of its
' only parameter is U, which is not yet defined.
Dim genMethod As MethodBuilder = _
myType.DefineMethod("GM", _
MethodAttributes.Public Or MethodAttributes.Static)
Dim methodParamNames() As String = { "U" }
Dim methodParams As GenericTypeParameterBuilder() = _
genMethod.DefineGenericParameters(methodParamNames)
' Now add a signature for genMethod, specifying U
' as the type of the parameter. There is no return value
' and no custom modifiers.
genMethod.SetSignature(Nothing, Nothing, Nothing, _
New Type() { methodParams(0) }, Nothing, Nothing)
' Emit a method body for the generic method.
Dim ilg As ILGenerator = genMethod.GetILGenerator()
' Construct the type Sample(Of U) using MakeGenericType.
Dim SampleOfU As Type = _
myType.MakeGenericType(methodParams(0))
' Create a local variable to store the instance of
' Sample(Of U).
ilg.DeclareLocal(SampleOfU)
' Call the default constructor. Note that it is
' necessary to have the default constructor for the
' constructed generic type Sample(Of U); use the
' TypeBuilder.GetConstructor method to obtain this
' constructor.
Dim ctorOfU As ConstructorInfo = _
TypeBuilder.GetConstructor(SampleOfU, ctor)
ilg.Emit(OpCodes.Newobj, ctorOfU)
' Store the instance in the local variable; load it
' again, and load the parameter of genMethod.
ilg.Emit(OpCodes.Stloc_0)
ilg.Emit(OpCodes.Ldloc_0)
ilg.Emit(OpCodes.Ldarg_0)
' In order to store the value in the field of the
' instance of Sample(Of U), it is necessary to have
' a FieldInfo representing the field of the
' constructed type. Use TypeBuilder.GetField to
' obtain this FieldInfo.
Dim FieldOfU As FieldInfo = _
TypeBuilder.GetField(SampleOfU, myField)
' Store the value in the field.
ilg.Emit(OpCodes.Stfld, FieldOfU)
' Load the instance, load the field value, box it
' (specifying the type of the type parameter, U),
' and print it.
ilg.Emit(OpCodes.Ldloc_0)
ilg.Emit(OpCodes.Ldfld, FieldOfU)
ilg.Emit(OpCodes.Box, methodParams(0))
Dim writeLineObj As MethodInfo = _
GetType(Console).GetMethod("WriteLine", _
New Type() {GetType(Object)})
ilg.EmitCall(OpCodes.Call, writeLineObj, Nothing)
ilg.Emit(OpCodes.Ret)
' Emit an entry point method; this must be in a
' non-generic type.
Dim dummy As TypeBuilder = _
myModule.DefineType("Dummy", _
TypeAttributes.Class Or TypeAttributes.NotPublic)
Dim entryPoint As MethodBuilder = _
dummy.DefineMethod("Main", _
MethodAttributes.Public Or MethodAttributes.Static, _
Nothing, Nothing)
ilg = entryPoint.GetILGenerator()
' In order to call the static generic method GM, it is
' necessary to create a constructed type from the
' generic type definition for Sample. This can be ANY
' constructed type; in this case Sample(Of Integer)
' is used.
Dim SampleOfInt As Type = _
myType.MakeGenericType(GetType(Integer))
' Next get a MethodInfo representing the static generic
' method GM on type Sample(Of Integer).
Dim SampleOfIntGM As MethodInfo = _
TypeBuilder.GetMethod(SampleOfInt, genMethod)
' Next get a MethodInfo for GM(Of String), which is the
' instantiation of generic method GM that is called
' by Sub Main.
Dim GMOfString As MethodInfo = _
SampleOfIntGM.MakeGenericMethod(GetType(String))
' Finally, emit the call. Push a string onto
' the stack, as the argument for the generic method.
ilg.Emit(OpCodes.Ldstr, "Hello, world!")
ilg.EmitCall(OpCodes.Call, GMOfString, Nothing)
ilg.Emit(OpCodes.Ret)
myType.CreateType()
dummy.CreateType()
myAssembly.SetEntryPoint(entryPoint)
myAssembly.Save(myAsmName.Name & ".exe")
Console.WriteLine(myAsmName.Name & ".exe has been saved.")
End Sub
End Class
備註
方法 GetField 提供一種方式來取得 FieldInfo 對象，這個物件代表建構泛型型別的欄位，其泛型型別定義是由 TypeBuilder 物件表示。
例如，假設您有一個 TypeBuilder 物件，代表Visual Basic中 C# 語法 (G(Of T) 中的類型G<T>、 generic <T> ref class G C++) 中的物件，以及FieldBuilder代表Visual Basic 中 C# 語法 (Public F As T 中字段的 物件public T F，public: T F在 C++) 中G<T>定義。
G<T>假設具有型別參數U的泛型方法，它會建立建構型G<U>別的實例，並在該實例上呼叫字段F。 若要發出函式呼叫，您需要 FieldInfo 在建構型別上表示 F 的 物件，換句話說，該物件的類型不是 型 U 別 T。 若要這樣做，請先在 物件上TypeBuilder呼叫 MakeGenericType 方法，並GenericTypeParameterBuilder指定 表示U為型別自變數的物件。 然後使用 方法的MakeGenericType傳回值做為 參數，以及FieldBuilder表示F為 參數 fieldtype 的物件，呼叫 GetField 方法。 傳回值是 FieldInfo 您需要發出函數調用的物件。 此程式代碼範例示範此案例。
適用於
GetField(String, BindingFlags)
傳回指定之名稱所指定的欄位。
public:
override System::Reflection::FieldInfo ^ GetField(System::String ^ name, System::Reflection::BindingFlags bindingAttr);public override System.Reflection.FieldInfo? GetField (string name, System.Reflection.BindingFlags bindingAttr);public override System.Reflection.FieldInfo GetField (string name, System.Reflection.BindingFlags bindingAttr);override this.GetField : string * System.Reflection.BindingFlags -> System.Reflection.FieldInfoPublic Overrides Function GetField (name As String, bindingAttr As BindingFlags) As FieldInfo參數
- name
- String
要取得的欄位名稱。
- bindingAttr
- BindingFlags
這必須是來自 BindingFlags 的位元旗標，像是在 InvokeMethod、NonPublic 等等一樣。
傳回
傳回 FieldInfo 物件，代表此類別所宣告或繼承的欄位，並且具有指定的名稱和公用或非公用的修飾詞。 如果沒有符合項目，會傳回 null。
例外狀況
不會為不完整的類型實作此方法。
備註
使用 或 Assembly.GetType 擷Type.GetType取類型，並在擷取的類型上使用反映。
