ListInitExpression Class

Definition

Namespace:

System.Linq.Expressions

Assembly:

System.Linq.Expressions.dll

Source:

ListInitExpression.cs

Represents a constructor call that has a collection initializer.

public ref class ListInitExpression sealed : System::Linq::Expressions::Expression

public sealed class ListInitExpression : System.Linq.Expressions.Expression

type ListInitExpression = class
    inherit Expression

Public NotInheritable Class ListInitExpression
Inherits Expression

Inheritance

Object

Expression

ListInitExpression

Examples

The following example creates a ListInitExpression that represents the initialization of a new dictionary instance that has 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")}

Dim tree1 As String = "maple"
Dim tree2 As String = "oak"

Dim addMethod As System.Reflection.MethodInfo = _
    Type.GetType("System.Collections.Generic.Dictionary`2[System.Int32, System.String]").GetMethod("Add")

' Create two ElementInit objects that represent the
' two key-value pairs to add to the Dictionary.
Dim elementInit1 As System.Linq.Expressions.ElementInit = _
    System.Linq.Expressions.Expression.ElementInit( _
        addMethod, _
        System.Linq.Expressions.Expression.Constant(tree1.Length), _
        System.Linq.Expressions.Expression.Constant(tree1))
Dim elementInit2 As System.Linq.Expressions.ElementInit = _
    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(Of Integer, String).
Dim newDictionaryExpression As System.Linq.Expressions.NewExpression = _
    System.Linq.Expressions.Expression.[New](Type.GetType("System.Collections.Generic.Dictionary`2[System.Int32, System.String]"))

' Create a ListInitExpression that represents initializing
' a new Dictionary(Of T) instance with two key-value pairs.
Dim listInitExpression As System.Linq.Expressions.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")

Remarks

Use the ListInit factory methods to create a ListInitExpression.

The value of the NodeType property of a ListInitExpression is ListInit.

Properties

CanReduce	Gets a value that indicates whether the expression tree node can be reduced.
Initializers	Gets the element initializers that are used to initialize a collection.
NewExpression	Gets the expression that contains a call to the constructor of a collection type.
NodeType	Returns the node type of this Expression.
Type	Gets the static type of the expression that this Expression represents.

Methods

Accept(ExpressionVisitor)	Dispatches to the specific visit method for this node type. For example, MethodCallExpression calls the VisitMethodCall(MethodCallExpression). (Inherited from Expression)
Equals(Object)	Determines whether the specified object is equal to the current object. (Inherited from Object)
GetHashCode()	Serves as the default hash function. (Inherited from Object)
GetType()	Gets the Type of the current instance. (Inherited from Object)
MemberwiseClone()	Creates a shallow copy of the current Object. (Inherited from Object)
Reduce()	Reduces the binary expression node to a simpler expression.
ReduceAndCheck()	Reduces this node to a simpler expression. If CanReduce returns true, this should return a valid expression. This method can return another node which itself must be reduced. (Inherited from Expression)
ReduceExtensions()	Reduces the expression to a known node type (that is not an Extension node) or just returns the expression if it is already a known type. (Inherited from Expression)
ToString()	Returns a textual representation of the Expression. (Inherited from Expression)
Update(NewExpression, IEnumerable<ElementInit>)	Creates a new expression that is like this one, but using the supplied children. If all of the children are the same, it will return this expression.
VisitChildren(ExpressionVisitor)	Reduces the node and then calls the visitor delegate on the reduced expression. The method throws an exception if the node is not reducible. (Inherited from Expression)