C# Execute Code Only If Other Code Was Successful

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1 C# Execute code only if other code was successful

Problem Description:

Say I have

Method1(); // might return error
Method2(); // should only be executed if previous line successful

I could use try and catch, however I still want errors to happen, I just don’t want Method2() to be run if any errors occurred.

Solution – 1

There is a "template" for functions that looks like this:

bool TrySomething( out int returnValue )

which return true if successful and false if not. The returnValue is only valid if the returned bool is true. So you can use those like this:

if( TrySomething(out int someValue) )
{
     Method2( someValue );
}

The various TryParse methods of different types are examples of that.

Another approach would be if Method1 throws an exception:

Method1();
// If Method1 throws an exception, Method2 will not be executed.
// The control flow will be redirected to the "next" catch block
// that handles the exception type or if none of those exist crash 
// the app.
Method2();

So, even if you do not surround this with a try/catch block and Method1 throws, the control flow will not move on to execute Method2.

If you do use a try/catch block, Method2 will also not be executed:

try
{
    Method1(); // throws 
    Method2(); // won't execute
}
catch(SomeException ex)
{
    // Control flow will continue here.
    // Handle that exception
}
finally // optional
{
    // This will be executed regardless of whether there was an exception or not.
}

For further reading:

Exceptions and Exception Handling

Solution – 2

As suggested by @ProgrammingLlama you should do something like this:

     try {
        MethodWithErrorOrException();
        MethodAfter();
     }
     catch (Exception) {
        // Handling
     }
     finally {
        MethodAlwaysCalled();
     }

Naturally MethodWithErrorOrException() should rise Exception.

Alternatively you have to use a return value to the method MethodWithErrorOrException() to understand if everything was successful, but it is not the most elegant solution.

Solution – 3

Make Method1 return false on error.
Than you can use it like this:

if(Method1()){Method2();}

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