DropDownList与重复的数据值字段OnSelected得到困惑，并选择第一个为什么？

问题描述

当前问题：我的DropDownList随DataTextField =COLUMNS_NAMEDataValueField =DATA_TYPE属性一起提供，DropDownList_SelectedIndexChanged（）不会根据所选输入保留文本。但是它保留了项目列表中的第一个值

需要解决方案：如何根据DATA_TYPE属性保留所选的输入文本？ 我尝试存储会话[DDLValue] = DropDownList.SelectedItem.Text ，但它始终保留来自索引中存在的相应DATA_TYPE的项目列表中的第一个值。

ie如果我从以下DropDownList输入中选择e，DropDownList中保留的值为d

保留e

  COLUMN_NAME DATA_TYPE 
a decimal 
b decimal 
c decimal 
d int 
e int 
f varchar 
g varchar 
h varchar 
i varchar 
j varchar 
  / pre> 
 
 
 Aspx代码：
 < asp：DropDownList ID =DropDownList5runat =serverAutoPostBack =trueOnSelectedIndexChanged =DropDownList5_SelectedIndexChangedDataSourceID =MySqlDataSource> 
< / asp：DropDownList> 
< asp：SqlDataSource ID =MySqlDataSourcerunat =server> 
< / asp：SqlDataSource> 
  
 C＃代码：
  protected void Page_Load（object sender，EventArgs e）
 {
 if（！IsPostBack）
 {
 BindDropDownLists（）; 
} 
} 
 
 private void BindDropDownLists（）
 {
 MySqlDataSource.ConnectionString = connection; 
 MySqlDataSource.SelectCommand =SELECT DATA_TYPE +'_'+ convert（varchar（10），ROW_NUMBER（）OVER（ORDER BY DATA_TYPE））作为DATA_TYPE，COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE（TABLE_NAME ='RESULT'AND COLUMN_NAME IN（'Column1'，'column2'，'Column3'））; 
 
 DropDownList5.DataTextField =COLUMN_NAME; 
 DropDownList5.DataValueField =DATA_TYPE; 
 DropDownList5.DataBind（）; 
 
} 
  
 
 
解决方案
 ，您的下拉列表如下所示，需要使用唯一的值字段进行正确选择  
 
Current Issue: My DropDownList is provided with DataTextField="COLUMNS_NAME" DataValueField="DATA_TYPE" properties, the DropDownList_SelectedIndexChanged() does not retain the text based on the selected input. But it retains the first value from the list of items
Solution Required: How to Retain the selected input text based on the DATA_TYPE property ? I tried storing the Session["DDLValue"] = DropDownList.SelectedItem.Text but it always retains the first value from the list of items which satisfies the respective DATA_TYPE present in an Index.
i.e. if i choose "e" from The following DropDownList inputs the value retained in DropDownList is "d"
How to retain "e" 
COLUMN_NAME  DATA_TYPE  
a            decimal
b            decimal
c            decimal
d            int
e            int
f            varchar
g            varchar  
h            varchar
i            varchar
j            varchar
Aspx Code:
<asp:DropDownList ID="DropDownList5" runat="server"  AutoPostBack="true" OnSelectedIndexChanged ="DropDownList5_SelectedIndexChanged" DataSourceID="MySqlDataSource">
</asp:DropDownList>
<asp:SqlDataSource ID="MySqlDataSource" runat="server">
</asp:SqlDataSource>
C# code:
protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        BindDropDownLists();
    }
}

private void BindDropDownLists()
{
    MySqlDataSource.ConnectionString = connection;
    MySqlDataSource.SelectCommand =  "SELECT DATA_TYPE + '_' + convert(varchar(10), ROW_NUMBER() OVER(ORDER BY DATA_TYPE ))as DATA_TYPE, COLUMN_NAME FROM INFORMATION_SCHEMA.COLUMNS WHERE (TABLE_NAME = 'RESULT' AND COLUMN_NAME IN ('Column1','column2','Column3'))";

    DropDownList5.DataTextField = "COLUMN_NAME";
    DropDownList5.DataValueField = "DATA_TYPE";
    DropDownList5.DataBind();

}
 解决方案 
After render , your drop down list is look like below , need to use unique value field  for proper selection
                        
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