How to Update, Insert, Gridview Values to SQl DB

<asp:GridView ID="GridView1" runat="server"  DataKeyNames="EmpNo"
            AllowPaging="true" AllowSorting="true" PageSize="5"
            onpageindexchanging="GridView1_PageIndexChanging"
            onrowcancelingedit="GridView1_RowCancelingEdit"
            onrowdeleting="GridView1_RowDeleting" onrowediting="GridView1_RowEditing"
            onrowupdating="GridView1_RowUpdating"
            onselectedindexchanged="GridView1_SelectedIndexChanged"
            onsorting="GridView1_Sorting" EnableModelValidation="true"
            AutoGenerateColumns="false" onrowcommand="GridView1_RowCommand"
            ShowFooter="true" onrowdatabound="GridView1_RowDataBound">
            <RowStyle HorizontalAlign="Center" />
            <AlternatingRowStyle BackColor="White" />
            <EditRowStyle BackColor="#7C6F57" />
            <FooterStyle BackColor="#1C5E55" ForeColor="White" Font-Bold="True" />
            <HeaderStyle BackColor="#1C5E55" Font-Bold="True" ForeColor="White" />
            <PagerStyle BackColor="#666666" ForeColor="White" HorizontalAlign="Center" />
            <RowStyle BackColor="#E3EAEB" />
            <SelectedRowStyle BackColor="#C5BBAF" Font-Bold="True" ForeColor="#333333" />

           <Columns>
<asp:TemplateField HeaderText="EmpNo" SortExpression="EmpNo" HeaderStyle-HorizontalAlign="Left"><EditItemTemplate>
<asp:TextBox ID="txtEmNo" runat="server" Text='<%#Eval("EmpNo") %>'></asp:TextBox>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="txtEmpNo" runat="server"/>
</FooterTemplate>
<ItemTemplate>
<asp:Label ID="lblitemNo" runat="server" Text='<%#Eval("EmpNo") %>'/>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="EmpName" SortExpression="EmpName" HeaderStyle-HorizontalAlign="Left">
<EditItemTemplate>
<asp:TextBox ID="txtEmpName" runat="server" Text='<%#Eval("EmpName") %>'></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator6" runat="server" ControlToValidate="txtEmpName" ValidationGroup="Add New"  ErrorMessage="Must Enter Emp Name"></asp:RequiredFieldValidator>
<span><asp:RegularExpressionValidator ID="RegExpValidator" runat="server" ControlToValidate="txtEmpName" ValidationGroup="Add New" ValidationExpression="^[A-Z a-z]+$" ErrorMessage="Only Charecters and white space are allowed">
</asp:RegularExpressionValidator></span>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="txtEmpName" runat="server"/>
<asp:RequiredFieldValidator ID="RequiredFieldValidator6" runat="server" ControlToValidate="txtEmpName" ValidationGroup="Add New"  ErrorMessage="Must Enter Emp Name"></asp:RequiredFieldValidator>
<span><asp:RegularExpressionValidator ID="RegExpValidator" runat="server" ControlToValidate="txtEmpName" ValidationGroup="Add New" ValidationExpression="^[A-Z a-z]+$" ErrorMessage="Only Charecters and white space are allowed">
</asp:RegularExpressionValidator></span>
</FooterTemplate>
<ItemTemplate>
<asp:Label ID="lblitemName" runat="server" Text='<%#Eval("EmpName") %>'/>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Designation" HeaderStyle-HorizontalAlign="Left" SortExpression="Designation">
<ItemTemplate><%# Eval("Designation") %></ItemTemplate>
<EditItemTemplate>
<asp:DropDownList ID="dropDesg" runat="server" SelectedValue='<%# Eval("Designation").ToString() %>'>
<asp:ListItem Selected="True">Select Designation</asp:ListItem>
<asp:ListItem Text="Manager" Value="Manager"></asp:ListItem>
<asp:ListItem Text="Asis Manager" Value="Asis Manager"></asp:ListItem>
<asp:ListItem Text="Sales Rep" Value="Sales Rep"></asp:ListItem>
</asp:DropDownList>
</EditItemTemplate>
<FooterTemplate>
<asp:DropDownList ID="dropDesg" runat="server">
<asp:ListItem Selected="True">Select Designation</asp:ListItem>
<asp:ListItem Text="Manager" Value="Manager"></asp:ListItem>
<asp:ListItem Text="Asis Manager" Value="Asis Manager"></asp:ListItem>
<asp:ListItem Text="Sales Rep" Value="Sales Rep"></asp:ListItem>
</asp:DropDownList>
</FooterTemplate>
</asp:TemplateField>

<%--<asp:TemplateField HeaderText="Designation" SortExpression="Designation"><EditItemTemplate>
<asp:TextBox ID="txtDesg" runat="server" Text='<%#Eval("Designation") %>'></asp:TextBox>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="txtDesg" runat="server"/>
</FooterTemplate>
<ItemTemplate>
<asp:Label ID="lblitemDesg" runat="server" Text='<%#Eval("Designation") %>'/>
</ItemTemplate>
</asp:TemplateField>--%>
<%--<asp:TemplateField HeaderText="Department" SortExpression="Department"><EditItemTemplate>
<asp:TextBox ID="txtDep" runat="server" Text='<%#Eval("Department") %>'></asp:TextBox>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="txtDep" runat="server"/>
</FooterTemplate>
<ItemTemplate>
<asp:Label ID="lblitemDep" runat="server" Text='<%#Eval("Department") %>'/>
</ItemTemplate>
</asp:TemplateField>--%>

<asp:TemplateField HeaderText="Department" HeaderStyle-HorizontalAlign="Left" SortExpression="Department">
<ItemTemplate><%# Eval("Department") %></ItemTemplate>
<EditItemTemplate>
<asp:DropDownList ID="ddlDep" runat="server" SelectedValue='<%# Eval("Department").ToString() %>'>
<asp:ListItem Selected="True">Select Department</asp:ListItem>
<asp:ListItem Text="Accounts" Value="Accounts"></asp:ListItem>
<asp:ListItem Text="Sales" Value="Sales"></asp:ListItem>
</asp:DropDownList>
</EditItemTemplate>
<FooterTemplate>
<asp:DropDownList ID="ddlDep" runat="server">
<asp:ListItem Selected="True">Select Department</asp:ListItem>
<asp:ListItem Text="Accounts" Value="Accounts"></asp:ListItem>
<asp:ListItem Text="Sales" Value="Sales"></asp:ListItem>
</asp:DropDownList>
</FooterTemplate>
</asp:TemplateField>

<asp:TemplateField HeaderText="Salary" HeaderStyle-HorizontalAlign="Left"><EditItemTemplate>
<asp:TextBox ID="txtSal" runat="server" ValidationGroup="Add New" Text='<%#Eval("Salary") %>'></asp:TextBox>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="txtSal" runat="server" ValidationGroup="Add New"/>
<asp:RequiredFieldValidator ID="ReqGV5" runat="server" ValidationGroup="Add New"
        ControlToValidate="txtSal"
        ErrorMessage=" Enter salary with numeric values"></asp:RequiredFieldValidator>
<span>
    <asp:RangeValidator ID="RangeGV1" runat="server"
        Type="Double" ValidationGroup="Add New" ControlToValidate="txtSal"
        MinimumValue="10000.00" MaximumValue="60000.00"
        ErrorMessage =" Must be in the range between 20000.00 to 50000.00"></asp:RangeValidator></span>
</FooterTemplate>
<ItemTemplate>
<asp:Label ID="lblitemSal" runat="server" Text='<%#Eval("Salary") %>'/>
</ItemTemplate>
</asp:TemplateField>
<%--<asp:TemplateField HeaderText="Gender" SortExpression="Gender"><EditItemTemplate>
<asp:TextBox ID="txtGen" runat="server"  Text='<%#Eval("Gender") %>'></asp:TextBox>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="txtGen" runat="server"/>
</FooterTemplate>
<ItemTemplate>
<asp:Label ID="lblitemGen" runat="server" Text='<%#Eval("Gender") %>'/>
</ItemTemplate>
</asp:TemplateField>--%>

<asp:TemplateField HeaderText="Gender" HeaderStyle-HorizontalAlign="Left">
<ItemTemplate>
<%# Eval("Gender")%>
</ItemTemplate>
<EditItemTemplate>
<asp:RadioButtonList ID="RBLGender" runat="server" RepeatDirection="Horizontal" SelectedValue='<%# Eval("Gender") %>'>
<asp:ListItem Value="Male">Male</asp:ListItem>
<asp:ListItem Value="Female">Female</asp:ListItem>
</asp:RadioButtonList>
</EditItemTemplate>
<FooterTemplate>
<asp:RadioButtonList ID="RBLGender" runat="server">
<asp:ListItem Value="Male">Male</asp:ListItem>
<asp:ListItem Value="Female">Female</asp:ListItem>
</asp:RadioButtonList>
</FooterTemplate>
</asp:TemplateField>

<%--<asp:TemplateField HeaderText="Preference"  SortExpression="Preference"><EditItemTemplate>
<asp:TextBox ID="txtPref" runat="server" Text='<%#Eval("Preference") %>'></asp:TextBox>
</EditItemTemplate>
<FooterTemplate>
<asp:TextBox ID="txtPref" runat="server"/>
</FooterTemplate>
<ItemTemplate>
<asp:Label ID="lblitemPref" runat="server" Text='<%#Eval("Preference") %>'/>
</ItemTemplate>
</asp:TemplateField>--%>

<asp:TemplateField HeaderText="Preference" HeaderStyle-HorizontalAlign="Left">
<ItemTemplate><%# Eval("Preference") %></ItemTemplate>
<EditItemTemplate>
<asp:CheckBoxList ID="CheckBoxList1" runat="server" SelectedValue='<%# Eval("Preference").ToString() %>'>
<asp:ListItem>Coffee</asp:ListItem>
<asp:ListItem>Tea</asp:ListItem>
<asp:ListItem>Cool Drink</asp:ListItem>
</asp:CheckBoxList>
</EditItemTemplate>
<FooterTemplate>
<asp:CheckBoxList ID="CheckBoxList1" runat="server">
<asp:ListItem>Coffee</asp:ListItem>
<asp:ListItem>Tea</asp:ListItem>
<asp:ListItem>Cool Drink</asp:ListItem>
</asp:CheckBoxList>
</FooterTemplate>
</asp:TemplateField>