Expression.Parameter Method

Definition

Namespace:

System.Linq.Expressions

Assemblies:

netstandard.dll, System.Linq.Expressions.dll

Creates a ParameterExpression node that can be used to identify a parameter or a variable in an expression tree.

Overloads

Parameter(Type, String)	Creates a ParameterExpression node that can be used to identify a parameter or a variable in an expression tree.
Parameter(Type)	Creates a ParameterExpression node that can be used to identify a parameter or a variable in an expression tree.

Parameter(Type, String)

Source:

ParameterExpression.cs

Creates a ParameterExpression node that can be used to identify a parameter or a variable in an expression tree.

C#

public static System.Linq.Expressions.ParameterExpression Parameter(Type type, string? name);

Parameters

type

Type

The type of the parameter or variable.

name

String

The name of the parameter or variable, used for debugging or printing purpose only.

Returns

ParameterExpression

A ParameterExpression that has the NodeType property equal to Parameter and the Type and Name properties set to the specified values.

Exceptions

ArgumentNullException

type is null.

Parameter(Type)

Source:

ParameterExpression.cs

Creates a ParameterExpression node that can be used to identify a parameter or a variable in an expression tree.

C#

public static System.Linq.Expressions.ParameterExpression Parameter(Type type);

Parameters

type

Type

The type of the parameter or variable.

Returns

ParameterExpression

A ParameterExpression node with the specified name and type.

Examples

The following example demonstrates how to create a MethodCallExpression object that prints the value of a ParameterExpression object.

C#

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

// Creating a parameter for the expression tree.
ParameterExpression param = Expression.Parameter(typeof(int));

// Creating an expression for the method call and specifying its parameter.
MethodCallExpression methodCall = Expression.Call(
    typeof(Console).GetMethod("WriteLine", new Type[] { typeof(int) }),
    param
);

// The following statement first creates an expression tree,
// then compiles it, and then runs it.
Expression.Lambda<Action<int>>(
    methodCall,
    new ParameterExpression[] { param }
).Compile()(10);

// This code example produces the following output:
//
// 10