Validate at-least one DropDownList Item selected inside ASP.Net Repeater using C# and VB.Net

Hi bittu500,

Refer below sample.

HTML

C#

<table id="tbl1" class="table table-bordered table-scrollable table-condensed">
    <thead>
        <tr>
            <th style="font-size: smaller;">SN</th>
            <th style="font-size: smaller;">Country</th>
        </tr>
    </thead>
    <tbody>
        <asp:Repeater runat="server" ID="rptr1" OnItemDataBound="rptr1_OnItemDataBound">
            <ItemTemplate>
                <tr>
                    <td class="text-align-center"><%# (((RepeaterItem)Container).ItemIndex+1).ToString()%> </td>
                    <td class="text-align-left">
                        <asp:DropDownList ID="ddl1" runat="server"></asp:DropDownList>
                    </td>
                </tr>
            </ItemTemplate>
        </asp:Repeater>
    </tbody>
</table>
<div>
    <asp:Button ID="btnSubmit" OnClick="btnSave_Click" runat="server" Text="Save & Submit" CausesValidation="false" />
</div>

VB.Net

<table id="tbl1" class="table table-bordered table-scrollable table-condensed">
    <thead>
        <tr>
            <th style="font-size: smaller;">SN</th>
            <th style="font-size: smaller;">Country</th>
        </tr>
    </thead>
    <tbody>
        <asp:Repeater runat="server" ID="rptr1" OnItemDataBound="rptr1_OnItemDataBound">
            <ItemTemplate>
                <tr>
                    <td class="text-align-center"><%#((CType(Container, RepeaterItem)).ItemIndex + 1).ToString()%> </td>
                    <td class="text-align-left">
                        <asp:DropDownList ID="ddl1" runat="server"></asp:DropDownList>
                    </td>
                </tr>
            </ItemTemplate>
        </asp:Repeater>
    </tbody>
</table>
<div>
    <asp:Button ID="btnSubmit" runat="server" OnClick="btnSave_Click" Text="Save & Submit" CausesValidation="false" />
</div>

Namespaces

C#

using System.Data;

VB.Net

Imports System.Data

Code

C#

protected void Page_Load(object sender, EventArgs e)
{
    if (!this.IsPostBack)
    {
        DataTable dt = GetData();
        rptr1.DataSource = dt;
        rptr1.DataBind();
    }
}

private DataTable GetData()
{
    DataTable dt = new DataTable();
    dt.Columns.AddRange(new DataColumn[3] {
            new DataColumn("Id"),
            new DataColumn("Name"),
            new DataColumn("Country")
        });
    dt.Rows.Add(1, "John Hammond", "United States");
    dt.Rows.Add(2, "Mudassar Khan", "India");
    dt.Rows.Add(3, "Suzanne Mathews", "France");
    dt.Rows.Add(4, "Robert Schidner", "Russia");
    return dt;
}

protected void rptr1_OnItemDataBound(object sender, RepeaterItemEventArgs e)
{
    if (e.Item.ItemType == ListItemType.Item || e.Item.ItemType == ListItemType.AlternatingItem)
    {
        DataTable dtnew = GetData();
        DropDownList ddl1 = (e.Item.FindControl("ddl1") as DropDownList);
        ddl1.DataSource = dtnew;
        ddl1.DataTextField = "Country";
        ddl1.DataValueField = "Country";
        ddl1.DataBind();
        ddl1.Items.Insert(0, new ListItem { Text = "Select", Value = "" });
        string country = (e.Item.DataItem as DataRowView)["Country"].ToString();
        if (ddl1.Items.FindByValue(country) != null)
        {
            ddl1.Items.FindByValue(country).Selected = true;
        }
    }
}

protected void btnSave_Click(object sender, System.EventArgs e)
{
    List<string> selected = new List<string>();
    foreach (RepeaterItem item in rptr1.Items)
    {
        string selectedValue = (item.FindControl("ddl1") as DropDownList).SelectedValue;
        if (!string.IsNullOrEmpty(selectedValue))
        {
            selected.Add(selectedValue);
        }
    }
    if (selected.Count == 0)
    {
        ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('Please select atleast an option.');", true);
    }
}

VB.Net

Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
    If Not Me.IsPostBack Then
        Dim dt As DataTable = GetData()
        rptr1.DataSource = dt
        rptr1.DataBind()
    End If
End Sub

Private Function GetData() As DataTable
    Dim dt As DataTable = New DataTable()
    dt.Columns.AddRange(New DataColumn(2) {
                        New DataColumn("Id"),
                        New DataColumn("Name"),
                        New DataColumn("Country")})
    dt.Rows.Add(1, "John Hammond", "United States")
    dt.Rows.Add(2, "Mudassar Khan", "India")
    dt.Rows.Add(3, "Suzanne Mathews", "France")
    dt.Rows.Add(4, "Robert Schidner", "Russia")
    Return dt
End Function

Protected Sub rptr1_OnItemDataBound(ByVal sender As Object, ByVal e As RepeaterItemEventArgs)
    If e.Item.ItemType = ListItemType.Item OrElse e.Item.ItemType = ListItemType.AlternatingItem Then
        Dim dtnew As DataTable = GetData()
        Dim ddl1 As DropDownList = (TryCast(e.Item.FindControl("ddl1"), DropDownList))
        ddl1.DataSource = dtnew
        ddl1.DataTextField = "Country"
        ddl1.DataValueField = "Country"
        ddl1.DataBind()
        ddl1.Items.Insert(0, New ListItem With {.Text = "Select", .Value = ""})
        Dim country As String = (TryCast(e.Item.DataItem, DataRowView))("Country").ToString()
        If ddl1.Items.FindByValue(country) IsNot Nothing Then
            ddl1.Items.FindByValue(country).Selected = True
        End If
    End If
End Sub

Protected Sub btnSave_Click(ByVal sender As Object, ByVal e As System.EventArgs)
    Dim selected As List(Of String) = New List(Of String)()
    For Each item As RepeaterItem In rptr1.Items
        Dim selectedValue As String = (TryCast(item.FindControl("ddl1"), DropDownList)).SelectedValue
        If Not String.IsNullOrEmpty(selectedValue) Then
            selected.Add(selectedValue)
        End If
    Next
    If selected.Count = 0 Then
        ClientScript.RegisterStartupScript(Me.GetType(), "alert", "alert('Please select atleast an option.');", True)
    End If
End Sub

Screenshot