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Expression.Block Method (IEnumerable<ParameterExpression>, IEnumerable<Expression>)

Creates a BlockExpression that contains the given variables and expressions.

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

public static BlockExpression Block(
	IEnumerable<ParameterExpression> variables,
	IEnumerable<Expression> expressions
)

Parameters

variables
Type: System.Collections.Generic.IEnumerable<ParameterExpression>
The variables in the block.
expressions
Type: System.Collections.Generic.IEnumerable<Expression>
The expressions in the block.

When the block expression is executed, it returns the value of the last expression in the block.

The following code example shows how to pass a parameter to a block expression and process this parameter within a block.


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


       // This block has a parameter expression
       // that represents a variable within the block scope.
       // It assigns a value to the variable,
       // and then adds a constant to the assigned value. 

       ParameterExpression varExpr = Expression.Variable(typeof(int), "sampleVar");
       BlockExpression blockExpr = Expression.Block(
           new ParameterExpression[] { varExpr },
           Expression.Assign(varExpr, Expression.Constant(1)),
           Expression.Add(varExpr, Expression.Constant(5))
       );

       // Print out the expressions from the block expression.
       outputBlock.Text += "The expressions from the block expression:" + "\n";
       foreach (var expr in blockExpr.Expressions)
          outputBlock.Text += expr.ToString() + "\n";

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

       // This code example produces the following output:
       // The expressions from the block expression:
       // (sampleVar = 1)
       // (sampleVar + 5)
       // The result of executing the expression tree:
       // 6



Silverlight

Supported in: 5, 4

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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