TryExpression Class

Definition

Namespace:

System.Linq.Expressions

Assembly:

System.Linq.Expressions.dll

Source:

TryExpression.cs

Represents a try/catch/finally/fault block.

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

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

type TryExpression = class
    inherit Expression

Public NotInheritable Class TryExpression
Inherits Expression

Inheritance

Object

Expression

TryExpression

Examples

The following example demonstrates how to create a TryExpression object that contains a catch statement by using the TryCatch method.

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

// A TryExpression object that has a Catch statement.
// The return types of the Try block and all Catch blocks must be the same.
TryExpression tryCatchExpr =
    Expression.TryCatch(
        Expression.Block(
            Expression.Throw(Expression.Constant(new DivideByZeroException())),
            Expression.Constant("Try block")
        ),
        Expression.Catch(
            typeof(DivideByZeroException),
            Expression.Constant("Catch block")
        )
    );

// The following statement first creates an expression tree,
// then compiles it, and then runs it.
// If the exception is caught,
// the result of the TryExpression is the last statement
// of the corresponding Catch statement.
Console.WriteLine(Expression.Lambda<Func<string>>(tryCatchExpr).Compile()());

// This code example produces the following output:
//
// Catch block

' Add the following directive to the file:
' Imports System.Linq.Expressions 

' A TryExpression object that has a Catch statement.
' The return types of the Try block and all Catch blocks must be the same.
Dim tryCatchExpr As TryExpression =
       Expression.TryCatch(
           Expression.Block(
               Expression.Throw(Expression.Constant(New DivideByZeroException())),
               Expression.Constant("Try block")
           ),
           Expression.Catch(
               GetType(DivideByZeroException),
               Expression.Constant("Catch block")
           )
       )

' The following statement first creates an expression tree,
' then compiles it, and then runs it.
' If the exception is caught, 
' the result of the TryExpression is the last statement 
' of the corresponding Catch statement.
Console.WriteLine(Expression.Lambda(Of Func(Of String))(tryCatchExpr).Compile()())

' This code example produces the following output:
'
' Catch block

Remarks

The body block is protected by the try block.

The handlers consist of a set of CatchBlock expressions that can be either catch statements or filters.

The fault block runs if an exception is thrown.

The finally block runs regardless of how control exits the body.

Only one of fault or finally blocks can be supplied.

The return type of the try block must match the return type of any associated catch statements.

Properties

Body	Gets the Expression representing the body of the try block.
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)
Fault	Gets the Expression representing the fault block.
Finally	Gets the Expression representing the finally block.
Handlers	Gets the collection of CatchBlock expressions associated with the try block.
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 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(Expression, IEnumerable<CatchBlock>, Expression, Expression)	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)