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Expression.Switch Method (Expression, Expression, SwitchCase[])

Creates a SwitchExpression that represents a switch statement that has a default case.

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

public static SwitchExpression Switch(
	Expression switchValue,
	Expression defaultBody,
	params SwitchCase[] cases
)

Parameters

switchValue
Type: System.Linq.Expressions.Expression
The value to be tested against each case.
defaultBody
Type: System.Linq.Expressions.Expression
The result of the switch if switchValue does not match any of the cases.
cases
Type: System.Linq.Expressions.SwitchCase[]
The set of cases for this switch expression.

All SwitchCase objects in a SwitchExpression object must have the same type, unless the SwitchExpression has the type void.

Each SwitchCase object has an implicit break statement, which means that there is no implicit fall through from one case label to another.

If switchValue does not match any of the cases, the default case represented by defaultBody is run.

The following example demonstrates how to create an expression that represents a swtich statement that has a default case.


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

// An expression that represents the switch value.
ConstantExpression switchValue = Expression.Constant(3);

// This expression represents a switch statement 
// that has a default case.
SwitchExpression switchExpr =
    Expression.Switch(
        switchValue,
        Expression.Call(
                    null,
                    typeof(Console).GetMethod("WriteLine", new Type[] { typeof(String) }),
                    Expression.Constant("Default")
                ),
        new SwitchCase[] {
            Expression.SwitchCase(
                Expression.Call(
                    null,
                    typeof(Console).GetMethod("WriteLine", new Type[] { typeof(String) }),
                    Expression.Constant("First")
                ),
                Expression.Constant(1)
            ),
            Expression.SwitchCase(
                Expression.Call(
                    null,
                    typeof(Console).GetMethod("WriteLine", new Type[] { typeof(String) }),
                    Expression.Constant("Second")
                ),
                Expression.Constant(2)
            )
        }
    );

// The following statement first creates an expression tree,
// then compiles it, and then runs it.
Expression.Lambda<Action>(switchExpr).Compile()();

// This code example produces the following output:
//
// Default


.NET Framework

Supported in: 4

.NET Framework Client Profile

Supported in: 4

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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

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