DefaultExpression Class
[ This article is for Windows Phone 8 developers. If you’re developing for Windows 10, see the latest documentation. ]
Represents the default value of a type or an empty expression.
Assembly: System.Core (in System.Core.dll)
The DefaultExpression type exposes the following members.
| Name | Description | |
|---|---|---|
![]() | 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.) |
![]() | NodeType | Returns the node type of this expression. Extension nodes should return Extension when overriding this method. (Overrides Expression.NodeType.) |
![]() | 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.) |
![]() | 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 expression that represents a default value for a given type by using the Default method.
// Add the following directive to your file: // using System.Linq.Expressions; // This expression represents the default value of a type // (0 for integer, null for a string, etc.) Expression defaultExpr = Expression.Default( typeof(byte) ); // Print out the expression. outputBlock.Text += defaultExpr.ToString() + "\n"; // The following statement first creates an expression tree, // then compiles it, and then executes it. outputBlock.Text += Expression.Lambda<Func<byte>>(defaultExpr).Compile()() + "\n"; // This code example produces the following output: // // default(Byte) // 0
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