C sharp donet code to Get Single query Data

C sharp donet code to Get Single query Data . Use following code in common class .

 static public string getSingleQueryData(string _Querystr)  
     {  
       string Connstr= "";  
       OleDbConnection connection = null;  
       OleDbDataAdapter adp = null;  
       OleDbCommandBuilder oleDbCommandBuilder = null;  
       DataTable dataTable = null;  
       string _strReturn = "";  
       Connstr= ConfigurationSettings.AppSettings["strconnection"];  
       connection = new OleDbConnection(strconnection);  
       connection.Open();  
       adp = new OleDbDataAdapter(_Querystr, connection);  
       oleDbCommandBuilder = new OleDbCommandBuilder(adp);  
       dataTable = new DataTable();  
       adp.Fill(dataTable);  
       connection.Close();  
       if (dataTable.Rows.Count > 0)  
       {  
         _strReturn = dataTable.Rows[0][0].ToString();  
       }  
       return _strReturn;  
     }