SQL Server與C＃中數據庫的獨特連接

Question

我正在嘗試在設計中下拉框，但數據庫表類別中有重復項。 我試圖通過使用下面的代碼執行。 但是它沒有執行。 它只接收我更改過的所有命令的屬性：

cmd.CommandText = @"Select  Distinct Category_Desc from 
                    Database***name  order 
                    by Category_Desc";
adapter.SelectCommand = cmd;

SqlDataReader dr1 = cmd.ExecuteReader();

dr1.Read();

comboBoxCategory.ValueMember = "Category_Desc";
comboBoxCategory.DisplayMember = "Category_Desc";
comboBoxCategory.DataSource = dr1;

dr1.Dispose();

誰能幫忙如何從代碼中執行不同的查詢？

Answer 1

數據讀取器是僅向前的游標，您必須在最后一項之后迭代並關閉。請看此代碼段

            SqlDataReader dr1= command.ExecuteReader();
            ArrayList arl= new ArrayList();
            while (dr1.Read())
            {
             arl.Add(dr1("Category_Desc"));
            }

            dr1.close();
         //If its a winform project use this               
           string [] str = al.ToArray(typeof(string));
            FarPoint.Win.Spread.ComboBoxCellType cb = new 
             FarPoint.Win.Spread.ComboBoxCellType();
            cb.Items = arl;

Answer 2

使用適配器來填充數據表。 您已經有適配器，並且已經分配了SelectCommand。

adapter.SelectCommand = cmd;
System.Data.DataTable dtCategories = new System.Data.DataTable();
adapter.Fill(dtCategories);

comboBoxCategory.ValueMember = "Category_Desc";
comboBoxCategory.DisplayMember = "Category_Desc";
comboBoxCategory.DataSource = dtCategories;