ExpressionBuilder.GetCodeExpression 方法

定義

命名空間:

System.Web.Compilation

組件:

System.Web.dll

在衍生類別中覆寫時，傳回用來在頁面執行期間取得評估的運算式之程式碼。

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

表示由運算式繫結的屬性相關資訊之物件。

parsedData

Object

包含由 ParseExpression(String, Type, ExpressionBuilderContext) 傳回之剖析資料的物件。

context

ExpressionBuilderContext

用於評估運算式的內容資訊。

傳回

CodeExpression

CodeExpression，用於屬性指定。

範例

下列程式碼範例示範如何藉由覆寫 GetCodeExpression 方法傳回 CodeExpression 物件。

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

繼承自 類別的 ExpressionBuilder 類別必須實作 GetCodeExpression 抽象方法。

給實施者的注意事項

如果您實作自訂表格達式產生器，您必須為控制項屬性執行適當的類型轉換，並在 物件中 CodeExpression 傳回轉換作業。