Expression.Equal Method (Expression, Expression)

Creates a BinaryExpression that represents an equality comparison.

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

public static BinaryExpression Equal(
	Expression left,
	Expression right
)

Parameters

left
Type: System.Linq.Expressions.Expression

An Expression to set the Left property equal to.

right
Type: System.Linq.Expressions.Expression

An Expression to set the Right property equal to.

Return Value

Type: System.Linq.Expressions.BinaryExpression
A BinaryExpression that has the NodeType property equal to Equal and the Left and Right properties set to the specified values.

ExceptionCondition
ArgumentNullException

left or right is null.

InvalidOperationException

The equality operator is not defined for left.Type and right.Type.

The resulting BinaryExpression has the Method property set to the implementing method. The Type property is set to the type of the node. If the node is lifted, the IsLifted property is true. Otherwise, it is false. The IsLiftedToNull property is always false. The following information describes the implementing method, the node type, and whether a node is lifted.

The following rules determine the implementing method for the operation:

  • If the Type property of either left or right represents a user-defined type that overloads the equality operator, the MethodInfo that represents that method is the implementing method.

  • Otherwise, the implementing method is null.

If the implementing method is not null:

  • If left.Type and right.Type are assignable to the corresponding argument types of the implementing method, the node is not lifted. The type of the node is the return type of the implementing method.

  • If the following two conditions are satisfied, the node is lifted and the type of the node is Boolean:

    • left.Type and right.Type are both value types of which at least one is nullable and the corresponding non-nullable types are equal to the corresponding argument types of the implementing method.

    • The return type of the implementing method is Boolean.

If the implementing method is null:

  • If left.Type and right.Type are both non-nullable, the node is not lifted. The type of the node is Boolean.

  • If left.Type and right.Type are both nullable, the node is lifted. The type of the node is Boolean.

The following code example shows how to create an expression that checks whether the values of its two arguments are equal.

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

// This expression compares the values of its two arguments. 
// Both arguments need to be of the same type.
Expression equalExpr = Expression.Equal(
    Expression.Constant(42),
    Expression.Constant(45)
);

// Print out the expression.
Console.WriteLine(equalExpr.ToString());

// The following statement first creates an expression tree, 
// then compiles it, and then executes it.
Console.WriteLine(
    Expression.Lambda<Func<bool>>(equalExpr).Compile()());

// This code example produces the following output: 
// 
// (42 == 45) 
// False

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

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.

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