ExpressionBuilder.GetCodeExpression 方法

定義

命名空間:
System.Web.Compilation
組件:
System.Web.dll

當在衍生類別中覆寫時，會回傳在頁面執行時用來取得所值表達式的程式碼。

public:
 abstract System::CodeDom::CodeExpression ^ GetCodeExpression(System::Web::UI::BoundPropertyEntry ^ entry, System::Object ^ parsedData, System::Web::Compilation::ExpressionBuilderContext ^ context);
public abstract System.CodeDom.CodeExpression GetCodeExpression(System.Web.UI.BoundPropertyEntry entry, object parsedData, System.Web.Compilation.ExpressionBuilderContext context);
abstract member GetCodeExpression : System.Web.UI.BoundPropertyEntry * obj * System.Web.Compilation.ExpressionBuilderContext -> System.CodeDom.CodeExpression
Public MustOverride Function GetCodeExpression (entry As BoundPropertyEntry, parsedData As Object, context As ExpressionBuilderContext) As CodeExpression

參數

entry
BoundPropertyEntry

代表由該表達式綁定的性質資訊的物件。

parsedData
Object

包含解析資料的物件，由 ParseExpression(String, Type, ExpressionBuilderContext)返回。

context
ExpressionBuilderContext

用於表達式評估的情境資訊。

傳回

CodeExpression

CodeExpression A用於財產轉讓。

範例

以下程式碼範例示範如何覆寫GetCodeExpression該方法來回傳物件CodeExpression。

public override CodeExpression GetCodeExpression(BoundPropertyEntry entry, 
object parsedData, ExpressionBuilderContext context)
{
    Type type1 = entry.DeclaringType;
    PropertyDescriptor descriptor1 = TypeDescriptor.GetProperties(type1)[entry.PropertyInfo.Name];
    CodeExpression[] expressionArray1 = new CodeExpression[3];
    expressionArray1[0] = new CodePrimitiveExpression(entry.Expression.Trim());
    expressionArray1[1] = new CodeTypeOfExpression(type1);
    expressionArray1[2] = new CodePrimitiveExpression(entry.Name);
    return new CodeCastExpression(descriptor1.PropertyType, new CodeMethodInvokeExpression(new 
   CodeTypeReferenceExpression(base.GetType()), "GetEvalData", expressionArray1));
}

Public Overrides Function GetCodeExpression(ByVal entry _
   As BoundPropertyEntry, ByVal parsedData As Object, ByVal context _
   As ExpressionBuilderContext) As CodeExpression
    Dim type1 As Type = entry.DeclaringType
    Dim descriptor1 As PropertyDescriptor = _
       TypeDescriptor.GetProperties(type1)(entry.PropertyInfo.Name)
    Dim expressionArray1(2) As CodeExpression
    expressionArray1(0) = New CodePrimitiveExpression(entry.Expression.Trim())
    expressionArray1(1) = New CodeTypeOfExpression(type1)
    expressionArray1(2) = New CodePrimitiveExpression(entry.Name)
    Return New CodeCastExpression(descriptor1.PropertyType, _
       New CodeMethodInvokeExpression(New CodeTypeReferenceExpression _
       (MyBase.GetType()), "GetEvalData", expressionArray1))
End Function

備註

繼承該 ExpressionBuilder 類別的類別必須實作抽象 GetCodeExpression 方法。

給實施者的注意事項

如果你實作自訂表達式建構器，必須對控制屬性執行正確的類型casting，並在物件中回傳cast操作 CodeExpression 。

適用於