CheckBox inside GridView and handle its events to get records based on its Checked state

Step-1 : Create New Project

Go to File > New > Project > Select asp.net web forms application > Entry Application Name > Click OK.

Step-2: Add a Database.

Go to Solution Explorer > Right Click on App_Data folder > Add > New item > Select SQL Server Database Under Data > Enter Database name > Add.

Step-3: Create a table and insert data for shown in Gridview.

Open Database > Right Click on Table > Add New Table > Add Columns > Save > Enter table name > Ok.

Step-4: Add Entity Data Model.

Go to Solution Explorer > Right Click on Project name form Solution Explorer > Add > New item > Select ADO.net Entity Data Model under data > Enter model name > Add.
A popup window will come (Entity Data Model Wizard) > Select Generate from database > Next >
Chose your data connection > select your database > next > Select tables > enter Model Namespace > Finish.

Step-5: Add Web Page.

Go to Solution Explorer > Right Click on Project under solution explorer > Add > New item > Select Web Form using Master Page under web > Enter Name > > Select Master Page>Add.
(Complete Code in Source Code)

Here is HTML Code for Gridview

<asp:GridView ID="GridView1"  Width="500px" runat="server" AutoGenerateColumns="False" DataKeyNames="StudentID" BackColor="White" BorderColor="#CCCCCC" BorderStyle="None" BorderWidth="1px" CellPadding="4" ForeColor="Black" GridLines="Horizontal">
    <Columns>
        <asp:TemplateField >
            <HeaderTemplate>                   
                    &nbsp;&nbsp; <asp:CheckBox ID="chkCheckAll" runat="server" onclick="javascript:SelectAllCheckboxes(this)" />
            </HeaderTemplate>
            <ItemTemplate>
                &nbsp;&nbsp;<asp:CheckBox ID="chkCheck" runat="server" onclick="javascript:CheckedCheckboxes(this)" />
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField HeaderText="Student Name">
            <ItemTemplate>
                <asp:Label ID="lblStudentName" runat="server" Text='<%#Eval("StudentName") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField  HeaderText="Class">
            <ItemTemplate>
                <asp:Label ID="lblClass" runat="server" Text='<%#Eval("Class") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:TemplateField  HeaderText="Class">
            <ItemTemplate>
                <asp:Label ID="lblRollNo" runat="server" Text='<%#Eval("RollNo") %>'></asp:Label>
            </ItemTemplate>
        </asp:TemplateField>
    </Columns>
    <FooterStyle BackColor="#CCCC99" ForeColor="Black" />
    <HeaderStyle BackColor="#333333" Font-Bold="True" ForeColor="White" />
    <PagerStyle BackColor="White" ForeColor="Black" HorizontalAlign="Right" />
    <SelectedRowStyle BackColor="#CC3333" Font-Bold="True" ForeColor="White" />
    <SortedAscendingCellStyle BackColor="#F7F7F7" />
    <SortedAscendingHeaderStyle BackColor="#4B4B4B" />
    <SortedDescendingCellStyle BackColor="#E5E5E5" />
    <SortedDescendingHeaderStyle BackColor="#242121" />
</asp:GridView>

Step-6: Add Code For Populate Data.

Write the followings code in your page load event for fetch Data from Database and show in gridview.

PAGE LOAD CODE

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

And Here is the function code

private void populateData()
{
    using (MyDatabaseEntities dc = new MyDatabaseEntities())
    {
        GridView1.DataSource = dc.StudentMasters.ToList();
        GridView1.DataBind();
    }
}

Step-7: Add Javascript code for Select Gridview Record(s).

<script src="Scripts/jquery-1.7.1.js"></script>
<script language="javascript" type="text/javascript">
    function SelectAllCheckboxes(chk) {
        var totalRows = $("#<%=GridView1.ClientID %> tr").length;
        var selected = 0;
        $('#<%=GridView1.ClientID %>').find("input:checkbox").each(function () {
            if (this != chk) {
                this.checked = chk.checked;
                selected += 1;
            }
        });
    }
 
    function CheckedCheckboxes(chk) {
        if (chk.checked) {
            var totalRows = $('#<%=GridView1.ClientID %> :checkbox').length;
            var checked = $('#<%=GridView1.ClientID %> :checkbox:checked').length
            if (checked == (totalRows - 1)) {
                $('#<%=GridView1.ClientID %>').find("input:checkbox").each(function () {
                    this.checked = true;
                });
            }
            else {
                $('#<%=GridView1.ClientID %>').find('input:checkbox:first').removeAttr('checked');
            }
        }
        else {
            $('#<%=GridView1.ClientID %>').find('input:checkbox:first').removeAttr('checked');
        }
    }       
</script>

Step-8: Write following code in Button Click Event to get Selected records.  

protected void Button1_Click(object sender, EventArgs e)
{
    string Selected = "";
    foreach (GridViewRow gr in GridView1.Rows)
    {
        CheckBox cb = (CheckBox)gr.FindControl("chkCheck");
        Label lblName = (Label)gr.FindControl("lblStudentName");
        // You can get other value same way               
 
        if (cb != null && cb.Checked)
        {
            string StdID = GridView1.DataKeys[gr.DataItemIndex].Values["StudentID"].ToString();
            Selected += "Student ID : " + StdID + ", Name : " + lblName.Text.Trim() + "<br/>";
        }
    }
 
    lblResult.Text = Selected;
}

STEP-9: Run Application

Run Application and Get result in your browser