ExpressionServices.ConvertReference<TResult> Method
Definition
Important
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Converts a reference to a workflow environment-aware expression to an activity tree.
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))Type Parameters
- TResult
The type the expression is being converted to.
Parameters
- expression
- Expression<Func<ActivityContext,TResult>>
The expression being converted.
Returns
The converted expression.
Examples
The following two code examples illustrate the use of ConvertReference and Convert. The first code example uses ConvertReference in an Assign activity to convert a lambda expression into a string property that is assigned a value. Next, Convert is called to convert a lambda expression into a string property value that is printed to the console in the WriteLine activity.
// 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);
}
The following code example is like the previous one except that the expression to convert is a reference to an item in a multidimensional array.
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);
}
Remarks
The conversion methods in ExpressionServices are designed to work with variables and constants defined inside the workflow, or passed into the workflow via arguments.
