Summary of the difference between using throw and throw ex in C#

throw keyword:

Used to throw the current exception and retain the original exception stack information. When using the throw keyword, the stack information of the current exception is preserved, which is very useful for debugging and tracing exceptions.

For example:

try
{
    // Some code that may throw exceptions}
catch (Exception ex)
{
    // Handle exceptions    throw; // Rethrow the current exception, retaining the original exception stack information}

There are mainly the following usages of throw:

1. The first type

(It is not recommended to use it, but unfortunately many people have always used it like this). This will eat up the original exception point and reset the exception start point in the stack:

try
{
}
catch (Exception ex)
{
    throw ex;
}

2. The second type

It can be traced back to the original exception point, but the compiler warns that the defined ex is not used:

try
{
}
catch (Exception ex)
{
    throw;
}

3. The third type

Without exception parameters, this is actually the same as the second type, and can catch all types of exceptions, and the IDE will not alert:

try
{
}
catch 
{
    throw;
}

4. The fourth type

The exception is repackaged, but the original exception point information will be retained. Recommended use.

try
{
}
catch (Exception ex)
{
    throw new Exception("Abnormal further packaged", ex);
}

throw ex keyword:

Also used to throw the current exception, but reset the stack information of the exception. When using the throw ex keyword, the stack information of the current exception will be reset to the current position instead of retaining the original exception stack information. This can make debugging and tracing exceptions difficult.

For example:

try
{
    // Some code that may throw exceptions}
catch (Exception ex)
{
    // Handle exceptions    throw ex; // Rethrow the current exception and reset the stack information of the exception}

Therefore, it is recommended to use the throw keyword when handling exceptions to preserve the original exception stack information for better debugging and tracking of exceptions.

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