How to change return of function from string to generic list

Question

problem

How to change return of function from string to return generic list by using csharp ?

I have stored procedure name getcompanies return list of companies id as following

create proc getcompannies as select compnyid from companes where compnyid > 10

so that result will be as following
11
12
13
14
15
etc...
so that i need to change function below from string to return generic list to be dynamically using

What I have tried:

public static string ExecuteProcedureReturnString(string connString, string procName,
           params SqlParameter[] paramters)
       {
           string result = "";
           using (var sqlConnection = new SqlConnection(connString))
           {
               using (var command = sqlConnection.CreateCommand())
               {
                   command.CommandType = System.Data.CommandType.StoredProcedure;
                   command.CommandText = procName;
                   if (paramters != null)
                   {
                       command.Parameters.AddRange(paramters);
                   }
                   sqlConnection.Open();
                   var ret = command.ExecuteScalar();
                   if (ret != null)
                       result = Convert.ToString(ret);
               }
           }
           return result;
       }