You can build an expression tree which is throwing an exception by using Expression.Throw method. For example, you have the following code.
try
{
Console.WriteLine("Before throwing exception");
throw new DivideByZeroException();
Console.WriteLine("After throwing exception");
}
catch (DivideByZeroException)
{
Console.WriteLine("Catch block");
}
Here is the code that is required to build the same functionality using expression tree.
var tryBlock = Expression.Block(
WriteLineExpression("Before throwing exception"),
Expression.Throw(Expression.Constant(new DivideByZeroException())),
WriteLineExpression("After throwing exception")
);
var catchBlock = Expression.Catch(
typeof(DivideByZeroException),
WriteLineExpression("Catch block")
);
TryExpression tryCatchExpr = Expression.TryCatch(tryBlock, catchBlock);
Expression.Lambda<Action>(tryCatchExpr).Compile()();
This example shows how to create an expression that contains a goto statement. Here is the code for WriteLineExpression method
public static Expression WriteLineExpression(string s)
{
return Expression.Call(null,
typeof(Console).GetMethod("WriteLine", new Type[] { typeof(String) }),
Expression.Constant(s));
}