只要保持你的代码去 - 你在正确的轨道上：

  //调用SQL助手类来获得初始数据
 DataTable的DT = sql.ExecuteDataTable（sp_MyProc）; 

 dt.Columns.Add（NewColumn的typeof（System.Int32））; 

的foreach（DataRow的行中dt.Rows）
 {
 //需要设定值NewColumn柱
行[NewColumn] = 0; //或将其设置为其他值
} 

 //这里可能保存您的数据集，设置所有新的值
后 

How do I add a new DataColumn to a DataTable object that already contains data?

PseudoCode

//call SQL helper class to get initial data 
DataTable dt = sql.ExecuteDataTable("sp_MyProc");

dt.Columns.Add("NewColumn", type(System.Int32));

foreach(DataRow row in dr.Rows)
{
    //need to set value to NewColumn column
}

Just keep going with your code - you're on the right track:

//call SQL helper class to get initial data 
DataTable dt = sql.ExecuteDataTable("sp_MyProc");

dt.Columns.Add("NewColumn", typeof(System.Int32));

foreach(DataRow row in dt.Rows)
{
    //need to set value to NewColumn column
    row["NewColumn"] = 0;   // or set it to some other value
}

// possibly save your Dataset here, after setting all the new values