DefaultExpression Class
Represents the default value of a type or an empty expression.
Assembly: System.Core (in System.Core.dll)
| 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(ExpressionVisitor) | 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.) |
![]() | GetHashCode() | Serves as the default hash function. (Inherited from Object.) |
![]() | GetType() | |
![]() | 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(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.) |
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. Console.WriteLine(defaultExpr.ToString()); // The following statement first creates an expression tree, // then compiles it, and then executes it. Console.WriteLine( Expression.Lambda<Func<byte>>(defaultExpr).Compile()()); // This code example produces the following output: // // default(Byte) // 0
Available since 8
.NET Framework
Available since 4.0
Portable Class Library
Supported in: portable .NET platforms
Silverlight
Available since 4.0
Windows Phone Silverlight
Available since 8.0
Windows Phone
Available since 8.1
Any public static ( Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.


