[Solved] ASP.Net DropDownList set selected value not working

Hi makumbi,

Use FindByValue and check for not null before set Selected to True.

Please refer below sample.

HTML

<asp:GridView ID="gvStockBooks" runat="server" AutoGenerateColumns="false" OnRowDataBound="gvStockBooks_RowDataBound">
    <Columns>
        <asp:BoundField DataField="Account" HeaderText="Account" ReadOnly="true" />
        <asp:BoundField DataField="Name" HeaderText="Name" />
        <asp:BoundField DataField="Class" HeaderText="Class" />
        <asp:BoundField DataField="StdType" HeaderText="StdType" />
        <asp:BoundField DataField="Stream" HeaderText="Stream" />
        <asp:TemplateField HeaderText="Sex">
            <ItemTemplate>
                <asp:Label ID="lblSex" runat="server" Text='<%# Eval("Sex") %>' Visible="false"></asp:Label>
                    <asp:DropDownList ID="ddlsex" runat="server">
                    <asp:ListItem>MALE</asp:ListItem>
                    <asp:ListItem>FEMALE</asp:ListItem>
                </asp:DropDownList>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:BoundField DataField="Colour" HeaderText="Colour" />
        <asp:BoundField DataField="Acnos" HeaderText="ACNOS" />
    </Columns>
</asp:GridView>

Namespace

C#

using System.Data;

VB.Net

Imports Systems.Data

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        this.GridBind();
    }
}

private void GridBind()
{
    DataTable dt = new DataTable();
    dt.Columns.AddRange(new DataColumn[8]{new DataColumn("Account")
                                         ,new DataColumn("Name")
                                         ,new DataColumn("Class")
                                         ,new DataColumn("StdType")
                                         ,new DataColumn("Stream")
                                         ,new DataColumn("Sex")
                                         ,new DataColumn("Colour")
                                         ,new DataColumn("Acnos") });
    dt.Rows.Add("19-07485", "AAMILAH NYANZI GAJU", "P2", "Old", "W", "FEMALE", "Red", "01-18-144");
    dt.Rows.Add("15-05111", "AAYAN MOHAMMED", "P5", "Old", "G", "MALE", "Yellow", "01-15-270");
    dt.Rows.Add("19-07710", "ABAASA KINGSTON TUMWEBAZE", "P3", "Old", "L", "MALE", "Yellow", "02-17-203");
    dt.Rows.Add("16-05636", "ABAASA MARY", "P5", "Old", "H", "FEMALE", "Yellow", "01-15-244");
    dt.Rows.Add("14-04640", "ABAHO MELANIE", "P6", "Old", "D", "FEMALE", "Red", "01-14-041");
    dt.Rows.Add("20-02071", "ABAHO TROY MUSINGUZI", "P4", "New", "", "", "", "");
    dt.Rows.Add("16-05545", "ABAYO FRANCIS MELVIN ", "P5", "Old", "L", "MALE", "Red", "01-14-055");
    dt.Rows.Add("17-06484", "ABDOU HAKIM SECK", "P3", "Old", "C", "MALE", "Blue", "02-17-130");
    dt.Rows.Add("15-04806", "AGABA JEREMY", "P6", "Old", "D", "", "Green", "01-14-249");
    gvStockBooks.DataSource = dt;
    gvStockBooks.DataBind();
}

protected void gvStockBooks_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowType == DataControlRowType.DataRow)
    {
        DropDownList ddlSex = (e.Row.FindControl("ddlsex") as DropDownList);
        ddlSex.DataTextField = "Sex";
        ddlSex.DataValueField= "Sex";            
        ddlSex.DataBind();
        ddlSex.Items.Insert(0, new ListItem("please Select..", "0"));
        string sex = (e.Row.FindControl("lblSex") as Label).Text;
        if (ddlSex.Items.FindByValue(sex) != null)
        {
            ddlSex.Items.FindByValue(sex).Selected = true;
        }
    }
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Me.GridBind()
    End If
End Sub

Private Sub GridBind()
    Dim dt As DataTable = New DataTable()
    dt.Columns.AddRange(New DataColumn(7) {New DataColumn("Account"), New DataColumn("Name"), New DataColumn("Class"), New DataColumn("StdType"), New DataColumn("Stream"), New DataColumn("Sex"), New DataColumn("Colour"), New DataColumn("Acnos")})
    dt.Rows.Add("19-07485", "AAMILAH NYANZI GAJU", "P2", "Old", "W", "FEMALE", "Red", "01-18-144")
    dt.Rows.Add("15-05111", "AAYAN MOHAMMED", "P5", "Old", "G", "MALE", "Yellow", "01-15-270")
    dt.Rows.Add("19-07710", "ABAASA KINGSTON TUMWEBAZE", "P3", "Old", "L", "MALE", "Yellow", "02-17-203")
    dt.Rows.Add("16-05636", "ABAASA MARY", "P5", "Old", "H", "FEMALE", "Yellow", "01-15-244")
    dt.Rows.Add("14-04640", "ABAHO MELANIE", "P6", "Old", "D", "FEMALE", "Red", "01-14-041")
    dt.Rows.Add("20-02071", "ABAHO TROY MUSINGUZI", "P4", "New", "", "", "", "")
    dt.Rows.Add("16-05545", "ABAYO FRANCIS MELVIN ", "P5", "Old", "L", "MALE", "Red", "01-14-055")
    dt.Rows.Add("17-06484", "ABDOU HAKIM SECK", "P3", "Old", "C", "MALE", "Blue", "02-17-130")
    dt.Rows.Add("15-04806", "AGABA JEREMY", "P6", "Old", "D", "", "Green", "01-14-249")
    gvStockBooks.DataSource = dt
    gvStockBooks.DataBind()
End Sub

Protected Sub gvStockBooks_RowDataBound(ByVal sender As Object, ByVal e As GridViewRowEventArgs)
    If e.Row.RowType = DataControlRowType.DataRow Then
        Dim ddlSex As DropDownList = (TryCast(e.Row.FindControl("ddlsex"), DropDownList))
        ddlSex.DataTextField = "Sex"
        ddlSex.DataValueField = "Sex"
        ddlSex.DataBind()
        ddlSex.Items.Insert(0, New ListItem("please Select..", "0"))
        Dim sex As String = (TryCast(e.Row.FindControl("lblSex"), Label)).Text

        If ddlSex.Items.FindByValue(sex) IsNot Nothing Then
            ddlSex.Items.FindByValue(sex).Selected = True
        End If
    End If
End Sub

Screenshot