CODEWITHSUNDEEP
c#exception
user983738
user983738

Reputation: 1023

How Can I Force Execution to the Catch Block?

I am wondering can try..catch force execution to go into the catch and run code in there?

here example code:

try {
    if (AnyConditionTrue) {
      // run some code
    }
    else {
      // go catch
    }
} catch (Exception) {
    // run some code here...
}

Upvotes: 45

Views: 101329

Answers (12)

Jesse Williams
Jesse Williams

Reputation: 662

Slight resurrection, but I wanted to add both a sample (primarily like others) and a use case.

public int GetValueNum(string name)
    {
        int _ret = 0;

        try
        {
            Control c = (extendedControls.Single(s => s.ValueName == name) as Control);

            if (c.GetType() == typeof(ExtendedNumericUpDown))
                _ret = (int)((ExtendedNumericUpDown)c).Value;

            else
                throw new Exception();
        }

        catch
        {
            throw new InvalidCastException(String.Format("Invalid cast fetching .Value value for {0}.\nExtendedControllerListener.GetValueNum()", name));
        }

        return _ret;
    }

In my case, I have custom controls - a handful of controls that use a base Windows.Forms control, but add two bools and a string for tracking, and also automatically get registered to a Singleton List<T> so they can be properly fetched without drilling down through control containers (it's a tabbed form).

In this case, I'm creating some methods to easily get values (.Value, .Text, .Checked, .Enabled) by a name string. In the case of .Value, not all Control objects have it. If the extended control is not of type ExtendedNumericUpDown, it IS an InvalidCastException as the method should not be called against that type of control. This isn't flow, but the prescribed usage of invalid cast. Since Control doesn't naturally have a .Value property, Visual Studio won't let me just force an attempt and fail after.

Upvotes: 0

foyss
foyss

Reputation: 983

An effective way to throw an Exception and also jump to Catch as so:

try
{
   throw new Exception("Exception Message");
}
catch (Exception e)
{
   // after the throw, you will land here
}

Upvotes: 9

Muzafar Hasan
Muzafar Hasan

Reputation: 169

public class CustomException: Exception
{
     public CustomException(string message)
        : base(message) { }

}

// 

if(something == anything)
{
   throw new CustomException(" custom text message");
}

you can try this

Upvotes: 1

Marinha do Nascimento
Marinha do Nascimento

Reputation: 808

if(conditiontrue)
{

}
else{
    throw new Exception();
}

Upvotes: 2

Ian
Ian

Reputation: 3149

As cadrel said, but pass through an Exception to provide more feedback, which will be shown in the innerException:

try
{
    if (AnyConditionTrue)
    {
        MethodWhenTrue();
    }
    else
    {
        HandleError(new Exception("AnyCondition is not true"));
    }
}
catch (Exception ex)
{
    HandleError(ex);
}

... 

private void HandleError(Exception ex) {
    throw new ApplicationException("Failure!", ex);
}

Upvotes: 1

Mark Schultheiss
Mark Schultheiss

Reputation: 34168

I think what you want is a finally block: http://msdn.microsoft.com/en-us/library/zwc8s4fz(v=vs.80).aspx

see this

try
 {
     doSomething();
 }
catch
 {
     catchSomething();
     throw an error
 } 
finally
 {
     alwaysDoThis();
 }

This is different if/when you do this:

try
 {
     doSomething(); 
 }
 catch
 {
     catchSomething(); 
     throw an error
 }
  alwaysDoThis();// will not run on error (in the catch) condition

the the this last instance, if an error occurs, the catch will execute but NOT the alwaysDoThis();. Of course you can still have multiple catch as always.

Upvotes: 1

user596075
user596075

Reputation: 

   try{
      if (AnyConditionTrue){
              //run some code
               }
      else{
              throw new Exception();
          }
   }
   catch(){

      //run some code here...

   }

But like Yuck has stated, I wouldn't recommend this. You should take a step back at your design and what you're looking to accomplish. There's a better way to do it (i.e. with normal conditional flow, instead of exception handling).

Upvotes: 47

cadrell0
cadrell0

Reputation: 17307

Rather than throwing an Exception in the else, I would recommend extracting the code from your catch into a method and call that from your else

try
{
    if (AnyConditionTrue)
    {
        MethodWhenTrue();
    }
    else
    {
        HandleError();
    }
}
catch(Exception ex)
{
    HandleError();
}

Upvotes: 39

jug
jug

Reputation: 451

Yes, you have to throw exception :

  try
  {
    throw new Exception("hello");
  }
  catch (Exception)
  {

     //run some code here...
  }

Upvotes: 15

user1921
user1921

Reputation:

why are you catching an exception? Why not just run the code in your "else" block? If you MUST do it that way, just throw a new exception

throw new Exception();

Upvotes: 0

juergen d
juergen d

Reputation: 204766

You could throw an exception to force a catch

throw new Exception(...);

Upvotes: 0

mdm
mdm

Reputation: 12630

Yes, if you throw the exception that you intend to catch from within the try, it will be caught in the catch section.

I have to ask you why you would want to do this though? Exception handling is not meant to be a substitute for control flow.

Upvotes: 1

Related Questions