語言

ExpressionServices.ConvertReference<TResult> 方法

定義

命名空間:
System.Activities.Expressions
組件:
System.Activities.dll

將工作流程環境感知表達式的參考轉換為活動樹。

public:
generic <typename TResult>
 static System::Activities::Activity<System::Activities::Location<TResult> ^> ^ ConvertReference(System::Linq::Expressions::Expression<Func<System::Activities::ActivityContext ^, TResult> ^> ^ expression);
public static System.Activities.Activity<System.Activities.Location<TResult>> ConvertReference<TResult>(System.Linq.Expressions.Expression<Func<System.Activities.ActivityContext,TResult>> expression);
static member ConvertReference : System.Linq.Expressions.Expression<Func<System.Activities.ActivityContext, 'Result>> -> System.Activities.Activity<System.Activities.Location<'Result>>
Public Shared Function ConvertReference(Of TResult) (expression As Expression(Of Func(Of ActivityContext, TResult))) As Activity(Of Location(Of TResult))

類型參數

TResult

表達式被轉換成的類型。

參數

expression
Expression<Func<ActivityContext,TResult>>

這個表達正在轉換。

傳回

Activity<Location<TResult>>

那個被轉化的表情。

範例

以下兩個程式碼範例說明了 和 ConvertReference的使用Convert。 第一個程式碼範例在活動ConvertReference中將 Assign lambda 表達式轉換成一個字串屬性，並被指派一個值。 接著， Convert 呼叫 將 lambda 運算式轉換成字串屬性值，並列印到活動中的 WriteLine 主控台。

// Define a struct with a property named AProperty.
struct StructWithProperty
{
    public string AProperty { get; set; }
}

public static void ConvertReferenceForValueTypePropertyReferenceSample()
{
    // Create a variable of type StructWithProperty to store the property.
    var swpvar = new Variable<StructWithProperty>("swpvar", new StructWithProperty());

    Activity myActivity = new Sequence
    {
        Variables = { swpvar },
        Activities =
        {
            // Create an Assign activity to assign a value to the AProperty property.
            new Assign<string>
            {
                To = ExpressionServices.ConvertReference<string>(ctx => swpvar.Get(ctx).AProperty),
                // Assign a string literal to AProperty.
                Value = "Hello",
            },
            // Print the new property value to the console.
            new WriteLine()
            {
                Text = ExpressionServices.Convert<string>(ctx => swpvar.Get(ctx).AProperty),
            }
        }
    };

    // Invoke the Sequence activity.
    WorkflowInvoker.Invoke(myActivity);
}

以下的程式碼範例與前一個類似，但 convert 的運算式是多維陣列中的一個項目參考。

public static void ConvertReferenceForMultidimensionalArrayItemReferenceSample()
{
    // Create a variable to store a multidimensional array.
    var arrayvar = new Variable<int[,]>("arrayvar", new int[4, 5]);

    Activity myActivity = new Sequence
    {
        Variables = { arrayvar },
        Activities =
        {
            // Create an Assign activity to assign a value to the array item at index [1,2].
            new Assign<int>
            {
                To = ExpressionServices.ConvertReference<int>(ctx => arrayvar.Get(ctx)[1, 2]),
                // Assign an integer value to the array item at row 1 column 2.
                Value = 1,
            },
            // Print the array item value to the console.
            new WriteLine()
            {
                Text = ExpressionServices.Convert<string>(ctx => arrayvar.Get(ctx)[1, 2].ToString()),
            }
        }
    };

    // Invoke the Sequence activity.
    WorkflowInvoker.Invoke(myActivity);
}

備註

這些 ExpressionServices 轉換方法設計用來處理工作流程中定義的變數和常數，或透過參數傳遞到工作流程中。

適用於