How to get userID for username in ASMX webservice

Question

I'm trying to store a user's post into an access database through a web method. I want to store the logged-in user's username, user's post, and the post datetime.

So far, I can store an existing user post by hard coding. But I want to store posts by any logged-in users. I was told I need to get userID for username.

Thus, I've found and tried adding the following codes:

//GetUser() returns current user information
MembershipUser user = Membership.GetUser();

//Returns the UserID and converts to a string
string UserID = user.ProviderUserKey.ToString();

When I tried debugging with breakpoints, the first one was okay. But for the second one, VS 2010 said that "object reference not set to an instance of an object." How do I fix it?

VS suggested adding "new," which didn't work. It also suggested to catch NullReferenceException, but I don't know how to use the codes they provided:

public class EHClass
{
    void ReadFile(int index)
    {
        // To run this code, substitute a valid path from your local machine
        string path = @"UsersDB_in_App_Data";
        System.IO.StreamReader file = new System.IO.StreamReader(path);
        char[] buffer = new char[10];
        try
        {
            file.ReadBlock(buffer, index, buffer.Length);
        }
        catch (System.IO.IOException e)
        {
            Console.WriteLine("Error reading from {0}. Message = {1}", path, e.Message);
        }

        finally
        {
            if (file != null)
            {
                file.Close();
            }
        }
        // Do something with buffer...
    }

}

Can you give me suggestions of what I need to do, or an alternative way to go about getting userID for username?

Answer 1

You didn't indicate what type of MembershipUser you have, but the ProviderUserKey is totally dependent on the underlying data store.

For example, the sql membership provider stores this value as a GUID.

If there is a possibility that this property won't contain any useful data, then you need to test it for existence before accessing it:

//Returns the UserID and converts to a string
string UserID;
if ((myObject != null) && (myObject.ProviderUserKey != null)) {
    UserId = myObject.ProviderUserKey.ToString();
} else {
    UserId = String.Empty;
}

In addition, unless you are using WSE in a straight asmx web service, I don't think that the memebership provider will have any valid data to operate on.

If this is the case, you will probably need to switch to WCF or implement WSE (NOT recommended).