IndexExpression Class
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Represents indexing a property or array.
Assembly: System.Core (in System.Core.dll)
The IndexExpression type exposes the following members.
| Name | Description | |
|---|---|---|
![]() | Arguments | Gets the arguments that will be used to index the property or array. |
![]() | CanReduce | Indicates 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.) |
![]() | Indexer | Gets the PropertyInfo for the property if the expression represents an indexed property, returns null otherwise. |
![]() | NodeType | Returns the node type of this Expression. (Overrides Expression.NodeType.) |
![]() | Object | An object to index. |
![]() | Type | Gets the static type of the expression that this Expression represents. (Overrides Expression.Type.) |
| Name | Description | |
|---|---|---|
![]() | Accept | Dispatches to the specific visit method for this node type. For example, MethodCallExpression calls the VisitMethodCall. (Inherited from Expression.) |
![]() | Equals(Object) | Determines whether the specified Object is equal to the current Object. (Inherited from Object.) |
![]() | Finalize | Allows an object to try to free resources and perform other cleanup operations before the Object is reclaimed by garbage collection. (Inherited from Object.) |
![]() | GetHashCode | Serves as a hash function for a particular type. (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 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.) |
![]() | 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 | 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 | 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.) |
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.
outputBlock.Text += "Array Access Expression:" + "\n";
outputBlock.Text += arrayAccessExpr.ToString() + "\n";
outputBlock.Text += "Lambda Expression:" + "\n";
outputBlock.Text += lambdaExpr.ToString() + "\n";
outputBlock.Text += "The result of executing the lambda expression:" + "\n";
// 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.
outputBlock.Text += lambdaExpr.Compile().Invoke(new int[] { 10, 20, 30 }, 0, 5) + "\n";
// 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
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