How to Start a windows service and set username and password for it?

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C#

I have made a windows service that checks on another window service to check if it is running.If the service to be monitored has stopped I need to set a given set of username and password and restart that service.would it be possible to do that.I tried the following code but it doesnt work.

string objPath = string.Format("Win32_Service.Name='{0}'", serviceName);
using (ManagementObject service = new ManagementObject(new ManagementPath(objPath)))
{
   object[] wmiParams = new object[11];
   wmiParams[6] = username;
   wmiParams[7] = password;
   service.InvokeMethod("Change", wmiParams);
}