WCF 用户代码未处理的异常

Question

I'm developing a WCF service with C# and .NET Framework 4.0.

I have the following code:

public long CreateUser(string userName)
{
    try
    {
        if ((userName == null) ||
            (userName.Equals(string.Empty)))
            throw new ArgumentNullException();

        ...

    }
    catch (Exception ex)
    {
        resultCode = 3;
        throw ex;
    }

    ...

}

when userName == string.Empty debugger stops and a dialog said:

ArgumentNullException unhandled by user code.

How can I fix that?

UPDATE

I want to notify client that there was an error in server side.

Answer 1

You need to handle the exception when using the CreateUser method:

try
{
    myClass.CreateUser (user);

}
catch (ArgumentNullException ex)
{

}

Answer 2

I think it would be best to just do something like this at the top of your method rather than create and throw an exception.

if (string.IsNullOrEmpty(userName))
{
  //handle
}

Answer 3

I think String.IsNullOrEmpty() is the most clear way; but I'm not sure I understand the question.

Your IF is working; and your code is throwing the exception. So writting it with String.IsnullOrEmpty() won't change that.

Do you want to know how to 'handle' that exception?

Answer 4

If you want to notify the client use FaultException .

Answer 5

Handle the exception:-)

This is normal behavior.

Your client must call your method like so:

try {
   long result = myService.CreateUser(someVariable);
} catch (ArgumentNullException exc)
{
  // Your error-handling code here
}

If you don't want to handle the exception, but simply process the "error code" (which is a bad practice, definitely not recommended), then you should remove the "throw ex;" line from your code.

Answer 6

First, you should know about String.IsNullOrEmpty(), it's useful in the case you provided.

Second, you are throwing an exception up the stack. There needs to be a try/catch block further up that is catching the exception you're throwing. Here, the try/catch is doing you no good.

public long CreateUser(string userName)
{
        if (String.IsNullOrEmpty(userName))
            throw new ArgumentNullException();

        ...
}

then elsewhere,

try 
{
     someClass.CreateUser(userName);
}
catch (ArgumentNullException ex)
{
  ... error handling code here
}