Question

我有像这样的SQL查询

SELECT  DISTINCT CustomerName FROM  Customers

它返回了不同customerNames的列表，

如何在C＃

中列出这个

目前我在DataTable中获取结果，然后在列表中仅提取我所需的列。

private List<String> GetDistinctCustomerNames()
{
   var dataTable = new DataTable("ResultDataTable");
   using (var sqlCommand = new SqlCommand())
   {
      // set the connection for the commnad
       sqlCommand.Connection = sqlConnection;

       // assign the insert query as a text to the sql command
        sqlCommand.CommandText = "SELECT  DISTINCT CustomerName FROM  Customers";

        using (var sqlDataAdapter = new SqlDataAdapter())
        {
           sqlDataAdapter.SelectCommand = sqlCommand;
           dataTable.Load(sqlCommand.ExecuteReader());
        }

        if (dataTable.Columns.Contains("CustomerName"))
        {
           return (from DataRow dataRow in dataTable.Rows select dataRow["CustomerName"].ToString()).ToList();
        }

  return null;
}

但我觉得这不是一个好的解决方案。

Answer 1

您应该googling或更多 https://stackoverflow.com/a/19406319/2089368 ......

Answer 2

而不是让你回来，我会做一个foreach

ForEach(var element in DataTable.Rows)
   if(element.CustomerName != NULL)
      list.add(element.ToString()) 
      //To string is only needed if the db stores it as not an nvarchar or something like that

return list

Answer 3

从方法中获取列表后，您可以应用以下代码。

 // Get distinct elements and convert into a list again.
List<string> distinct = list.Distinct().ToList();

在列表中获取不同的列名称

3 个答案: