How to update and add new line in gridview in C# .

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C#

ASP

ASP.NET

Gridview

Idea is to : Edit,Update, add new row in gridview.

I have written the command for edit button but went wrong in update query.
And also how to add new next line in gridview.

below I have mentioned what I have tried so far. I'm getting execution error in
protected void GridView2_RowUpdating

What I have tried:

Program so far:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Data;
using System.Data.SqlClient;
using System.Drawing;

public partial class Default2 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            addins();
        }
    }

    protected void addins()
    {
        SqlConnection cn = new SqlConnection("Server=WINDOWS-PC\\SQLEXPRESS;database=payroll;Trusted_Connection=Yes;");
        SqlCommand cmd = new SqlCommand();
        cmd.CommandText = "select * from amount";
        cmd.Connection = cn;
        cn.Open();


        SqlDataAdapter da = new SqlDataAdapter(cmd);
        DataSet ds = new DataSet();
        da.Fill(ds);
        int count = ds.Tables[0].Rows.Count;
        cn.Close();

        if (ds.Tables[0].Rows.Count > 0)
        {
            GridView2.DataSource = ds;
            GridView2.DataBind();
        }
        else
        {
            ds.Tables[0].Rows.Add(ds.Tables[0].NewRow());
            GridView2.DataSource = ds;
            GridView2.DataBind();
            int cc = GridView2.Rows[0].Cells.Count;

            Label1.Text = "No Record";
        }
    }

    protected void GridView2_RowEditing(object sender, GridViewEditEventArgs e)
    {
        GridView2.EditIndex = e.NewEditIndex;
        addins();
    }

    protected void GridView2_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        int sno = Convert.ToInt32(GridView2.DataKeys[e.RowIndex].Value.ToString());
        GridViewRow row = (GridViewRow)GridView2.Rows[e.RowIndex];
       // TextBox sno = (TextBox)GridView2.Rows[e.RowIndex].FindControl("sno");
        TextBox particulars = (TextBox)GridView2.Rows[e.RowIndex].FindControl("part");
        TextBox quantity = (TextBox)GridView2.Rows[e.RowIndex].FindControl("qty");
        TextBox rate = (TextBox)GridView2.Rows[e.RowIndex].FindControl("rate");
        TextBox amount = (TextBox)GridView2.Rows[e.RowIndex].FindControl("amt");
        GridView2.EditIndex = -1;

        SqlConnection cn = new SqlConnection("Server=WINDOWS-PC\\SQLEXPRESS;database=payroll;Trusted_Connection=Yes;");
        SqlCommand cmd = new SqlCommand();
        cmd.CommandText = "update amount set part='" + particulars.Text + "', qty = '" + quantity.Text + "', rate = '" + rate.Text + "', amt = '" + amount.Text + "' where  sno ='" + sno + "',cn)";
        cmd.Connection = cn;
        cn.Open();
        
        cmd.ExecuteNonQuery();
        cn.Close();
        addins();
    }

    protected void GridView2_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
    {
        GridView2.EditIndex = -1;
            addins();
    }