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BlockExpression Class

Represents a block that contains a sequence of expressions where variables can be defined.

System.Object
  System.Linq.Expressions.Expression
    System.Linq.Expressions.BlockExpression

Namespace:  System.Linq.Expressions
Assembly:  System.Core (in System.Core.dll)

public class BlockExpression : Expression

The BlockExpression type exposes the following members.

  NameDescription
Public propertySupported by Portable Class LibrarySupported in .NET for Windows Store appsCanReduceIndicates that the node can be reduced to a simpler node. If this returns true, Reduce() can be called to produce the reduced form. (Inherited from Expression.)
Public propertySupported by Portable Class LibrarySupported in .NET for Windows Store appsExpressionsGets the expressions in this block.
Public propertySupported by Portable Class LibrarySupported in .NET for Windows Store appsNodeTypeReturns the node type of this expression. Extension nodes should return Extension when overriding this method. (Overrides Expression.NodeType.)
Public propertySupported by Portable Class LibrarySupported in .NET for Windows Store appsResultGets the last expression in this block.
Public propertySupported by Portable Class LibrarySupported in .NET for Windows Store appsTypeGets the static type of the expression that this Expression represents. (Overrides Expression.Type.)
Public propertySupported by Portable Class LibrarySupported in .NET for Windows Store appsVariablesGets the variables defined in this block.
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  NameDescription
Protected methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsAcceptDispatches to the specific visit method for this node type. For example, MethodCallExpression calls the VisitMethodCall. (Overrides Expression.Accept(ExpressionVisitor).)
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Protected methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsReduceReduces this node to a simpler expression. If CanReduce returns true, this should return a valid expression. This method can return another node which itself must be reduced. (Inherited from Expression.)
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsReduceAndCheckReduces this node to a simpler expression. If CanReduce returns true, this should return a valid expression. This method can return another node which itself must be reduced. (Inherited from Expression.)
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsReduceExtensionsReduces the expression to a known node type (that is not an Extension node) or just returns the expression if it is already a known type. (Inherited from Expression.)
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsToStringReturns a textual representation of the Expression. (Inherited from Expression.)
Public methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsUpdateCreates a new expression that is like this one, but using the supplied children. If all of the children are the same, it will return this expression.
Protected methodSupported by Portable Class LibrarySupported in .NET for Windows Store appsVisitChildrenReduces the node and then calls the visitor delegate on the reduced expression. The method throws an exception if the node is not reducible. (Inherited from Expression.)
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The Block methods can be used to create a BlockExpression.

The following code example shows how to create a block expression. The block expression consists of two MethodCallExpression objects and one ConstantExpression object.

// Add the following directive to your file: 
// using System.Linq.Expressions;   

// The block expression allows for executing several expressions sequentually. 
// When the block expression is executed, 
// it returns the value of the last expression in the sequence.
BlockExpression blockExpr = Expression.Block(
    Expression.Call(
        null,
        typeof(Console).GetMethod("Write", new Type[] { typeof(String) }),
        Expression.Constant("Hello ")
       ),
    Expression.Call(
        null,
        typeof(Console).GetMethod("WriteLine", new Type[] { typeof(String) }),
        Expression.Constant("World!")
        ),
    Expression.Constant(42)
);

Console.WriteLine("The result of executing the expression tree:");
// The following statement first creates an expression tree, 
// then compiles it, and then executes it.            
var result = Expression.Lambda<Func<int>>(blockExpr).Compile()();

// Print out the expressions from the block expression.
Console.WriteLine("The expressions from the block expression:");
foreach (var expr in blockExpr.Expressions)
    Console.WriteLine(expr.ToString());

// Print out the result of the tree execution.
Console.WriteLine("The return value of the block expression:");
Console.WriteLine(result);

// This code example produces the following output: 
// 
// The result of executing the expression tree: 
// Hello World! 

// The expressions from the block expression: 
// Write("Hello ")
// WriteLine("World!")
// 42 

// The return value of the block expression: 
// 42

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4

.NET Framework Client Profile

Supported in: 4

Portable Class Library

Supported in: Portable Class Library

.NET for Windows Store apps

Supported in: Windows 8

.NET for Windows Phone apps

Supported in: Windows Phone 8.1, Windows Phone 8, Silverlight 8.1

Windows Phone 8.1, Windows Phone 8, Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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