Expression.Label Method (Type)
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Creates a LabelTarget representing a label with the given type.
Namespace: System.Linq.Expressions
Assembly: System.Core (in System.Core.dll)
Syntax
'Declaration
Public Shared Function Label ( _
type As Type _
) As LabelTarget
public static LabelTarget Label(
Type type
)
Parameters
- type
Type: System.Type
The type of value that is passed when jumping to the label.
Return Value
Type: System.Linq.Expressions.LabelTarget
The new LabelTarget representing a label with the given type.
Examples
The following example demonstrates how to use a LabelTarget object in a loop expression.
' Add the following directive to the file:
' Imports System.Linq.Expressions
' Creating a parameter expression.
Dim value As ParameterExpression =
Expression.Parameter(GetType(Integer), "value")
' Creating an expression to hold a local variable.
Dim result As ParameterExpression =
Expression.Parameter(GetType(Integer), "result")
' Creating a label to jump to from a loop.
Dim label As LabelTarget = Expression.Label(GetType(Integer))
' Creating a method body.
Dim block As BlockExpression = Expression.Block(
New ParameterExpression() {result},
Expression.Assign(result, Expression.Constant(1)),
Expression.Loop(
Expression.IfThenElse(
Expression.GreaterThan(value, Expression.Constant(1)),
Expression.MultiplyAssign(result,
Expression.PostDecrementAssign(value)),
Expression.Break(label, result)
),
label
)
)
' Compile an expression tree and return a delegate.
Dim factorial As Integer =
Expression.Lambda(Of Func(Of Integer, Integer))(block, value).Compile()(5)
outputBlock.Text &= factorial & vbCrLf
' This code example produces the following output:
'
' 120
// Add the following directive to the file:
// using System.Linq.Expressions;
// Creating a parameter expression.
ParameterExpression value = Expression.Parameter(typeof(int), "value");
// Creating an expression to hold a local variable.
ParameterExpression result = Expression.Parameter(typeof(int), "result");
// Creating a label to jump to from a loop.
LabelTarget label = Expression.Label(typeof(int));
// Creating a method body.
BlockExpression block = Expression.Block(
new[] { result },
Expression.Assign(result, Expression.Constant(1)),
Expression.Loop(
Expression.IfThenElse(
Expression.GreaterThan(value, Expression.Constant(1)),
Expression.MultiplyAssign(result,
Expression.PostDecrementAssign(value)),
Expression.Break(label, result)
),
label
)
);
// Compile and run an expression tree.
int factorial = Expression.Lambda<Func<int, int>>(block, value).Compile()(5);
outputBlock.Text += factorial + "\n";
// This code example produces the following output:
//
// 120
Version Information
Silverlight
Supported in: 5, 4
Platforms
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.