string causes “reference not set to instance of object”

[MENACESKINZ]

I have this code, which is reading data from a databse, then assigns a url from the web.config file to a string.\[code\]bool isRequestCI = false; if (context.Request.QueryString["RequestCI"] != null) { isRequestCI = Convert.ToBoolean(context.Request.QueryString["RequestCI"].ToString()); } string GetFileInfo; if (isRequestCI) { GetFileInfo = "select [FileName],FileExtension,MD5Hash from ElementCIBinaryAttachments where CIBinaryFileID = " + binaryFileID; } else GetFileInfo = "select [FileName],FileExtension,MD5Hash from CaseFileBinaryAttachments where BinaryFileID = " + binaryFileID; SqlCommand comGetFileInfo = new SqlCommand(GetFileInfo, cnGetFile); SqlDataReader drFileInfo; cnGetFile.Open(); drFileInfo = comGetFileInfo.ExecuteReader(); string fileName = ""; string fileExtension = ""; string MD5Hash = ""; while (drFileInfo.Read()) { fileName = drFileInfo["FileName"].ToString().Trim(); fileExtension = drFileInfo["FileExtension"].ToString().Trim(); MD5Hash = drFileInfo["MD5Hash"].ToString().Trim(); } drFileInfo.Close(); cnGetFile.Close(); string MD5PathRequestCI = ConfigurationManager.AppSettings["CIUploadedFiles"].ToString() + MD5Hash.Substring(0, 3) + @"\" + MD5Hash.Substring(3, 3) + @"\" + MD5Hash.Substring(6, 3) + @"\" + MD5Hash.Substring(9);\[/code\]however, it is causing an exception at \[code\]string MD5PathRequestCI\[/code\] saying "reference not set to an instance of an object and I have no clue why. I never used to do that or am I missing something?