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Expression.ListInit Method (NewExpression, ElementInit[])

Creates a ListInitExpression that uses specified ElementInit objects to initialize a collection.

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

public static ListInitExpression ListInit(
	NewExpression newExpression,
	params ElementInit[] initializers
)

Parameters

newExpression
Type: System.Linq.Expressions.NewExpression

A NewExpression to set the NewExpression property equal to.

initializers
Type: System.Linq.Expressions.ElementInit[]

An array of ElementInit objects to use to populate the Initializers collection.

Return Value

Type: System.Linq.Expressions.ListInitExpression
A ListInitExpression that has the NodeType property equal to ListInit and the NewExpression and Initializers properties set to the specified values.

ExceptionCondition
ArgumentNullException

newExpression or initializers is null.

-or-

One or more elements of initializers is null.

ArgumentException

newExpression.Type does not implement IEnumerable.

The Type property of newExpression must represent a type that implements IEnumerable.

The Type property of the resulting ListInitExpression is equal to newExpression.Type.

The following example demonstrates how to use the ListInit(NewExpression, ElementInit[]) method to create a ListInitExpression that represents the initialization of a new dictionary instance with two key-value pairs.

string tree1 = "maple";
string tree2 = "oak";

System.Reflection.MethodInfo addMethod = typeof(Dictionary<int, string>).GetMethod("Add");

// Create two ElementInit objects that represent the 
// two key-value pairs to add to the Dictionary.
System.Linq.Expressions.ElementInit elementInit1 =
    System.Linq.Expressions.Expression.ElementInit(
        addMethod,
        System.Linq.Expressions.Expression.Constant(tree1.Length),
        System.Linq.Expressions.Expression.Constant(tree1));
System.Linq.Expressions.ElementInit elementInit2 =
    System.Linq.Expressions.Expression.ElementInit(
        addMethod,
        System.Linq.Expressions.Expression.Constant(tree2.Length),
        System.Linq.Expressions.Expression.Constant(tree2));

// Create a NewExpression that represents constructing 
// a new instance of Dictionary<int, string>.
System.Linq.Expressions.NewExpression newDictionaryExpression =
    System.Linq.Expressions.Expression.New(typeof(Dictionary<int, string>));

// Create a ListInitExpression that represents initializing 
// a new Dictionary<> instance with two key-value pairs.
System.Linq.Expressions.ListInitExpression listInitExpression =
    System.Linq.Expressions.Expression.ListInit(
        newDictionaryExpression,
        elementInit1,
        elementInit2);

Console.WriteLine(listInitExpression.ToString());

// This code produces the following output: 
// 
// new Dictionary`2() {Void Add(Int32, System.String)(5,"maple"),
// Void Add(Int32, System.String)(3,"oak")}

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

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

.NET Framework

Supported in: 3.5

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