Is there a difference in the order of writing catch blocks?

Yes, it exists. catch blocks are processed sequentially. More specific exceptions should come before more general ones.

try
{
    // Code that may throw an exception
}
// More specific exception
catch (System.FormatException ex)
{
    // Handle format error
}
// Less specific exception
catch (System.Exception ex)
{
    // Handle all other exceptions
}

If a more general exception is placed first, then the more specific catch block will never be reached for exceptions that are subclasses of the more general one. For example, FormatException is a subclass of Exception. If catch (Exception ex) is first, it will catch FormatException as well.

Incorrect sequence:

try
{
    // Code that may throw an exception
}
// General exception
catch (System.Exception ex)
{
    // Handle all exceptions, including FormatException
}
// This block will never be reached for FormatException,
// because it is already caught by the previous block
catch (System.FormatException ex)
{
    // This code is unreachable in this case
}

The C# compiler will issue a warning or error for an unreachable catch block.