DropDownList with repeated data value fields OnSel

问题:

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();

}

回答1:

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

回答2:

I think the you should have unique values for the dropdown. You could try to fabricate the values which you could uniquely identify. Something like:

COLUMN_NAME  DATA_TYPE
a            a_decimal
b            b_decimal
c            c_decimal
d            d_int
e            e_int
f            f_varchar
g            g_varchar
h            h_varchar
i            i_varchar
j            j_varchar

A solution like this will ensure that you have unique values in your dropdown. The reason for using this is that creating DATA_TYPE string and extracting the actual value from it very simple. Just combine COLUMN_NAME and DATA_TYPE with underscore and split on underscore whenever the actual value is required.

The crux: You should try to have unique value for the dropdown. It could be an ID or some other unique value.

Please take this as a starting point and not as a copy paste solution.

回答3:

As you have duplicate values in data value field the problem is occurring. It is looking for the first match and selecting it.

If you want to continue with this then you may prefix some auto-increment integer and add it in value field and use substring to get the original value.

回答4:

Correct Solution : Thanks to @Kumar Manish comments

Select Command inside the BindDropDownLists()

private void BindDropDownLists()
     {
         SqlDataSource.ConnectionString = connection;

         SqlDataSource.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();
     }