how to add hex string to windows registry?

hear i have a hex value, i don't know what was the original value just this :

[HKEY_LOCAL_MACHINE\SOFTWARE\ESET\ESET Security\CurrentVersion\Plugins\01000400\Profiles\@My profile]
"Username"="test"
"Password"=hex:50,d6,e6,e9,ee,f0,cf,f2,6e,64,03,ad

I want to add these values to registry, I tried using command promp with administrator Privileges with the following command for username :

REG ADD HKEY_LOCAL_MACHINE\SOFTWARE\ESET\ESET Security\CurrentVersion\Plugins\01000400\Profiles\@My profile /v Username /d test /f

it worked like a charm. Then I added the following line to app.manifest File in VS2010 :

in order to get administrative privileges and I used the following :

private string GETCMD(string com)
    {
        string tempGETCMD = null;
        Process CMDprocess = new Process();
        System.Diagnostics.ProcessStartInfo StartInfo = new System.Diagnostics.ProcessStartInfo();
        StartInfo.FileName = "cmd"; //starts cmd window
        StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
        StartInfo.CreateNoWindow = true;
        StartInfo.RedirectStandardInput = true;
        StartInfo.RedirectStandardOutput = true;
        StartInfo.UseShellExecute = false; //required to redirect
        CMDprocess.StartInfo = StartInfo;
        CMDprocess.Start();
        System.IO.StreamReader SR = CMDprocess.StandardOutput;
        System.IO.StreamWriter SW = CMDprocess.StandardInput;
        SW.WriteLine(com);
        //insert your other commands here
        SW.WriteLine("exit"); //exits command prompt window
        tempGETCMD = SR.ReadToEnd(); //returns results of the command window
        SW.Close();
        SR.Close();
        return tempGETCMD;
    } 

It returns that " The operation completed successfully " but nothing is changed in registry

I tried setting value directly to registry using c# functions but it didn't work.

whats wrong here?

how i can set these values to registry ?

 why it is working by command prompt when I type the command manually but not programmatic, even when the program is started as administrator?