What is the difference between using 'throw' and 'throw ex' in C#?

Difference in preserving the call stack of an exception.

throw ex recreates the exception, losing the original stack trace. This complicates debugging, as information about the origin of the initial error is lost.

try
{
    // Some code that throws an exception
    throw new InvalidOperationException("Original error");
}
catch (Exception ex)
{
    // Here, information about the original source of the InvalidOperationException is lost
    throw ex; 
}

throw rethrows the same exception, preserving the entire original call stack. This is the preferred way to handle exceptions for logging or additional processing without losing error context.

try
{
    // Some code that throws an exception
    throw new InvalidOperationException("Original error");
}
catch (Exception ex)
{
    // Here, all call stack information is preserved
    throw; 
}

Feature	throw ex	throw
Call stack	Overwritten with the current throw ex location	Preserves the original call stack
Information loss	Yes, original source info is lost	No
Usage purpose	Usually not recommended, except in specific cases	Recommended for rethrowing