SharePoint Pragmatically Obtaining NewForm and EditFormUrl

protected void Page_Load(object sender, EventArgs e)
{
      SPSite site = new SPSite("http://abc-pc");

      SPWeb web = site.RootWeb;
      SPList list = web.Lists["Employee"];

      ListBox1.Items.Add(list.DefaultNewFormUrl.ToString());
      ListBox1.Items.Add(list.DefaultEditFormUrl.ToString());
}

SharePoint Filling a GridView with List Information based on the DropDownList Selection

protected void Page_Load(object sender, EventArgs e)
 {
     if (!Page.IsPostBack)
     {
            SPSite site = new SPSite("http://abc-pc");

            SPWeb web = site.RootWeb;

           
            DropDownList1.DataSource = web.Lists;
            DropDownList1.DataTextField = "Title";
            DropDownList1.DataBind();
            
    }
}

protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
{
     SPSite site = new SPSite("http://abc-pc");

     SPWeb web = site.RootWeb;
     SPList list = web.Lists[DropDownList1.Text];
          
     var item = list.Items;
     GridView1.DataSource = item.GetDataTable();
     GridView1.DataBind();
}

Programatically adding items to SharePoint List

protected void btnAdd_Click(object sender, EventArgs e)
{
      SPSite site = new SPSite("http://abc-pc");

      SPWeb web = site.RootWeb;
      SPList list = web.Lists["Employee"];

      SPListItem li = list.Items.Add();
      li["Title"] = txtEmployeeName.Text;
      li["Location"] = txtLocation.Text;
      li.Update();
}