C# 以 Visual Form OleDb 访问连接 row/column OR 无效输出不存在数据

Question

我试图从 Access 表单中的单个单元格中获取文本值，但这段代码却给我 System.Data.OleDb.OleDbDataReader 作为输出。当我将 Sell 更改为 *，并将 Convert.ToString(cusReader) 更改为 Convert.ToString(cusReader.getValue(1)) 时，标题中出现错误。我该如何解决？谢谢，杰克。

 OleDbCommand cmd = new OleDbCommand("SELECT Sell FROM Product WHERE ID = " + Count, conn);
            OleDbDataReader cusReader = cmd.ExecuteReader();

            if (Count != 0)
            {
                labelInsertedExtra.Visible = true;
                labelInserted.Visible = true;
                labelInsertedExtra.Text = Convert.ToString(cusReader);
            }
            else
            {
                labelInsertedExtra.Visible = false;
                labelInserted.Visible = false;
            }
            cusReader.Close();

Answer 1

指数从0开始

   Convert.ToString(cusReader.getValue(0))

您应该将 dbnull 值测试为

      while (cusReader.Read())
      {

        if (Count != 0 && cusReader["Sell"] != DBNull.Value)
        {
            labelInsertedExtra.Visible = true;
            labelInserted.Visible = true;
            labelInsertedExtra.Text = cusReader["Sell"].ToString(); 
        }
        else
        {
            labelInsertedExtra.Visible = false;
            labelInserted.Visible = false;
        }

        break;
      }

C# 以 Visual Form OleDb 访问连接 row/column OR 无效输出不存在数据

C# to Access connection in Visual Form OleDb No data exists for the row/column OR invalid output

c#

oledb

ms-access