using catch for a customized situation

Is it possible to call catch for a spec开发者_StackOverflowial condition when you are inside of try without using system error? For instance if a value int value 1 and then I want to use "catch".

One of the biggest sins in programming:) Don't use exceptions for managing programming flow! Now to your question - the catch block can be called in case an exception is thrown.

Your wording is a bit confusing but I think this is what you want.

int value = GetValue();
try
{
    if (value == 1)
        throw new InvalidOperationException();
    HappyPath(value);
}
catch (InvalidOperationException)
{
    SadPath(value);
}

Incidentally using exceptions for control flow is not the best practice.

No. You should catch exceptions (you can filter them by type), and then inside catch block you can filter on any condition.

It is not possible in C# to throw an exception that doesn’t derive from Exception, even though the CLR allows it.

It is possible to catch such an exception, but it is not possible to access the object that was thrown:

try
{
    MethodThatThrows();
}
catch      // This catches everything, even objects not deriving from Exception
{
    // Process exception
}

As soon as you specify a variable (e.g. catch (Exception e)), C# requires that the type is Exception or derived from it.

I think you might be saying that you want to catch an exception only in specific circumstances, and pass it through in all other circumstances? In that case, you can just use an if to check for the condition and then throw to re-throw the exception:

try
{
    // ...
}
catch (Exception e)
{
    // If it’s any value other than 1, we’re not interested in the exception
    if (value != 1)
        throw;        // note: throw; *not* throw e;

    // Process the exception here
}