Checked range of CheckBoxes on GridView based on DropDownList selection in ASP.Net

Hi Sanxion,

Please refer below sample.

HTML

<div>
    Start CustomerId :
    <asp:DropDownList ID="ddlStar" runat="server" AppendDataBoundItems="true">
        <asp:ListItem Text="Select" Value="Select"></asp:ListItem>
        <asp:ListItem Text="1" Value="1"></asp:ListItem>
        <asp:ListItem Text="2" Value="2" Selected="True"></asp:ListItem>
        <asp:ListItem Text="3" Value="3"></asp:ListItem>
        <asp:ListItem Text="4" Value="4"></asp:ListItem>
    </asp:DropDownList>
    End CustomerId :
    <asp:DropDownList ID="ddlEnd" runat="server">
        <asp:ListItem Text="Select" Value="Select"></asp:ListItem>
        <asp:ListItem Text="1" Value="1"></asp:ListItem>
        <asp:ListItem Text="2" Value="2"></asp:ListItem>
        <asp:ListItem Text="3" Value="3" Selected="True"></asp:ListItem>
        <asp:ListItem Text="4" Value="4"></asp:ListItem>
    </asp:DropDownList>
    <asp:GridView ID="gvCustomers" runat="server" AutoGenerateColumns="false">
        <Columns>
            <asp:TemplateField>
                <ItemTemplate>
                    <asp:CheckBox ID="chk" runat="server" />
                </ItemTemplate>
            </asp:TemplateField>
            <asp:BoundField DataField="CustomerId" HeaderText="CustomerId" />
            <asp:BoundField DataField="Name" HeaderText="Name" />
            <asp:BoundField DataField="Country" HeaderText="Country" />
        </Columns>
    </asp:GridView>
    <asp:Button Text="Submit" runat="server" OnClick="Select" />
</div>

Namespaces

C#

using System.Data;
using System.Data.SqlClient;
using System.Configuration;

VB.Net

Imports System.Data.SqlClient
Imports System.Data

Code

C#

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

private void BindGrid()
{
    using (SqlConnection con = new SqlConnection(ConfigurationManager.ConnectionStrings["constr"].ConnectionString))
    {
        using (SqlCommand cmd = new SqlCommand("SELECT * FROM Customers", con))
        {
            using (SqlDataAdapter da = new SqlDataAdapter(cmd))
            {
                DataTable dt = new DataTable();
                da.Fill(dt);
                gvCustomers.DataSource = dt;
                gvCustomers.DataBind();
            }
        }
    }
}

protected void Select(object sender, EventArgs e)
{
    int startRow = Convert.ToInt32(ddlStar.SelectedValue);
    int endRow = Convert.ToInt32(ddlEnd.SelectedValue);
    BindGrid();
    for (int i = startRow; i <= endRow; i++)
    {
        (gvCustomers.Rows[i - 1].FindControl("chk") as CheckBox).Checked = true;
    }
}

VB.Net

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

Private Sub BindGrid()
    Using con As SqlConnection = New SqlConnection(ConfigurationManager.ConnectionStrings("constr").ConnectionString)
        Using cmd As SqlCommand = New SqlCommand("SELECT * FROM Customers", con)

            Using da As SqlDataAdapter = New SqlDataAdapter(cmd)
                Dim dt As DataTable = New DataTable()
                da.Fill(dt)
                gvCustomers.DataSource = dt
                gvCustomers.DataBind()
            End Using
        End Using
    End Using
End Sub

Protected Sub [Select](ByVal sender As Object, ByVal e As EventArgs)
    Dim startRow As Integer = Convert.ToInt32(ddlStar.SelectedValue)
    Dim endRow As Integer = Convert.ToInt32(ddlEnd.SelectedValue)
    BindGrid()
    For i As Integer = startRow To endRow
        TryCast(gvCustomers.Rows(i - 1).FindControl("chk"), CheckBox).Checked = True
    Next
End Sub

Screenshot