IndexExpression Class

Represents indexing a property or array.

System.Object
  System.Linq.Expressions.Expression
    System.Linq.Expressions.IndexExpression

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

public sealed class IndexExpression : Expression

The IndexExpression type exposes the following members.

  NameDescription
Public propertySupported by Portable Class LibraryArgumentsGets the arguments that will be used to index the property or array.
Public propertySupported by Portable Class LibraryCanReduceIndicates that the node can be reduced to a simpler node. If this returns true, Reduce() can be called to produce the reduced form. (Inherited from Expression.)
Public propertySupported by Portable Class LibraryIndexerGets the PropertyInfo for the property if the expression represents an indexed property, returns null otherwise.
Public propertySupported by Portable Class LibraryNodeTypeReturns the node type of this Expression. (Overrides Expression.NodeType.)
Public propertySupported by Portable Class LibraryObjectAn object to index.
Public propertySupported by Portable Class LibraryTypeGets the static type of the expression that this Expression represents. (Overrides Expression.Type.)
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  NameDescription
Protected methodSupported by Portable Class LibraryAcceptDispatches to the specific visit method for this node type. For example, MethodCallExpression calls the VisitMethodCall. (Inherited from Expression.)
Public methodSupported by Portable Class LibraryEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Public methodSupported by Portable Class LibraryGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodSupported by Portable Class LibraryGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodSupported by Portable Class LibraryReduceReduces 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.)
Public methodSupported by Portable Class LibraryReduceAndCheckReduces 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.)
Public methodSupported by Portable Class LibraryReduceExtensionsReduces 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.)
Public methodSupported by Portable Class LibraryToStringReturns a textual representation of the Expression. (Inherited from Expression.)
Public methodSupported by Portable Class LibraryUpdateCreates 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.
Protected methodSupported by Portable Class LibraryVisitChildrenReduces 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.)
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The following code example shows how to create an object of the IndexExpression type and use it to change a value of an array element by using the ArrayAccess method.

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

            // This parameter expression represents a variable that will hold the array.
            ParameterExpression arrayExpr = Expression.Parameter(typeof(int[]), "Array");

            // This parameter expression represents an array index.            
            ParameterExpression indexExpr = Expression.Parameter(typeof(int), "Index");

            // This parameter represents the value that will be added to a corresponding array element.
            ParameterExpression valueExpr = Expression.Parameter(typeof(int), "Value");

            // This expression represents an array access operation. 
            // It can be used for assigning to, or reading from, an array element.
            Expression arrayAccessExpr = Expression.ArrayAccess(
                arrayExpr,
                indexExpr
            );

            // This lambda expression assigns a value provided to it to a specified array element. 
            // The array, the index of the array element, and the value to be added to the element 
            // are parameters of the lambda expression.
            Expression<Func<int[], int, int, int>> lambdaExpr = Expression.Lambda<Func<int[], int, int, int>>(
                Expression.Assign(arrayAccessExpr, Expression.Add(arrayAccessExpr, valueExpr)),
                arrayExpr,
                indexExpr,
                valueExpr
            );

            // Print out expressions.
            Console.WriteLine("Array Access Expression:");
            Console.WriteLine(arrayAccessExpr.ToString());

            Console.WriteLine("Lambda Expression:");
            Console.WriteLine(lambdaExpr.ToString());

            Console.WriteLine("The result of executing the lambda expression:");

            // The following statement first creates an expression tree, 
            // then compiles it, and then executes it. 
            // Parameters passed to the Invoke method are passed to the lambda expression.
            Console.WriteLine(lambdaExpr.Compile().Invoke(new int[] { 10, 20, 30 }, 0, 5));

            // This code example produces the following output: 
            // 
            // Array Access Expression: 
            // Array[Index] 

            // Lambda Expression: 
            // (Array, Index, Value) => (Array[Index] = (Array[Index] + Value)) 

            // The result of executing the lambda expression: 
            // 15

.NET Framework

Supported in: 4.6, 4.5, 4

.NET Framework Client Profile

Supported in: 4

Portable Class Library

Supported in: Portable Class Library

Supported in: Windows Phone 8.1

Supported in: Windows Phone Silverlight 8.1

Supported in: Windows Phone Silverlight 8

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.
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