Drag and drop a GridView control into your webpage and set its AutoGenerateColumns property as false. We are going to bind the GridView with the Customer Table from the database. The columns in the customer table are Customer Code [Cus_Code], Customer Name [Cus_Name], Gender [Cus_Sex], Age [Cus_Age], City [Cus_City] and Email Address [Cus_Email]. Specify the DataKeyNames as Cus_Code. Add 5 BoundField columns into the GridView and set its Data Field with the above column names. Add one CommandField column, make its command type as Edit/Update. Now convert all the BoundField fields in the GridView to TemplateField. So the every TemplateField will have a ItemTemplate section and EditItemTemplate section. ItemTemplate section will have a Asp.Net Label control binded to its corresponding column name. And EditItemTemplate section will have a TextBox control which is also binded to its corresponding column name.
For Customer Name column, we are going to put a static RequiredFieldValidator control at design time itself. So add a RequiredFieldValidator control into that column’s EditItemTemplate section. Specity its ControlToValidate property as TextBox1 and Error Message as “Name Required.”. For other columns such as Gender, we are going to use CustomValidator, for Age column we use RangeValidator, for Email we use RegularExpressionValidator and for City we use dynamic RequiredFieldValidator. Now the Html code of the GridView will look as follows

<asp:GridView ID="GridView1" runat="server" OnRowDataBound="GridView1_RowDataBound" AutoGenerateColumns="False" DataKeyNames="Cus_Code" OnRowCancelingEdit="GridView1_RowCancelingEdit" OnRowEditing="GridView1_RowEditing" OnRowUpdating="GridView1_RowUpdating">
<Columns>
<asp:TemplateField HeaderText="Name" SortExpression="Cus_Name">
<EditItemTemplate>
<asp:TextBox ID="t1" runat="server" Text='<%# Bind("Cus_Name") %>'></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" ControlToValidate="t1" ErrorMessage="Name Required"></asp:RequiredFieldValidator>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label1" runat="server" Text='<%# Bind("Cus_Name") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Gender">
<EditItemTemplate>
<asp:TextBox ID="t2" runat="server" Text='<%# Bind("Cus_Sex") %>' MaxLength="3" Width="50px"></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label5" runat="server" Text='<%# Bind("Cus_Sex") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Age" SortExpression="Cus_Age">
<EditItemTemplate>
<asp:TextBox ID="t3" runat="server" Text='<%# Bind("Cus_Age") %>' MaxLength="3" Width="50px"></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label3" runat="server" Text='<%# Bind("Cus_Age") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="Email" SortExpression="Cus_Email">
<EditItemTemplate>
<asp:TextBox ID="t4" runat="server" Text='<%# Bind("Cus_Email") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label4" runat="server" Text='<%# Bind("Cus_Email") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField HeaderText="City" SortExpression="Cus_City">
<EditItemTemplate>
<asp:TextBox ID="t5" runat="server" Text='<%# Bind("Cus_City") %>'></asp:TextBox>
</EditItemTemplate>
<ItemTemplate>
<asp:Label ID="Label2" runat="server" Text='<%# Bind("Cus_City") %>'></asp:Label>
</ItemTemplate>
</asp:TemplateField>
<asp:CommandField ShowEditButton="True" />
</Columns>
</asp:GridView>

Write a private method to fetch data from database as follows

login method:

private void BindGridView()
{ 
string sql = "Select * from CustomerTest Order By Cus_Name"; 
SqlDataAdapter da = new SqlDataAdapter(sql, “Yourconnectionstring”); 
DataTable dt = new DataTable(); 
da.Fill(dt);
GridView1.DataSource = dt; 
GridView1.DataBind();
} 

Enable GridView Edit and Cancel Events

In the RowEditing event of the GridView control, put the following code.

protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
{
GridView1.EditIndex = e.NewEditIndex;
BindGridView();
}