edit data in gridview asp.net entity framework

hello..

i am trying to edit the data in gridview....

my issues are:

redirect to same page and also i am geting a id which record i want to edit. but i want in fileupload which i already save image to be selected and also in dropdown the selected category shown when i redirect...

"form1" runat="server">
class="style1">
"fileUpload1" runat="server" />
Category:
"server" ID="ddlWallCategry" OnSelectedIndexChanged="ddlWallCategry_SelectedIndexChanged"
AutoPostBack="true" >

"btnSave" runat="server" Text="Save" OnClick="btnSave_Click" CssClass="btsave" />

"btnupdate" runat="server" Text="Update" OnClick="btnupdate_Click" CssClass="btsave" />

"GridViewCategory" runat="server" AutoGenerateColumns="False" DataKeyNames="Id"

AllowPaging="True"

OnPageIndexChanging="GridView1_PageIndexChanging"

OnRowEditing="GridViewCategory_RowEditing"

OnRowUpdating="GridViewCategory_RowUpdating"

OnRowDeleting ="GridViewCategory_RowDeleting">

"CategoryName" ItemStyle-Width="150">

"lblCategoryName" runat="server" Text='<%# Eval("CategoryName") %>'>

"TxtCategoryName" runat="server" Text='<%# Eval("CategoryName") %>'>

"Thumbnail" HeaderText="Thumbnail">

"100px" Width="100px" />

"Action">

"imgbtnEdit" runat="server" CommandName="Edit"

ImageUrl="~/img/edit.png" PostBackUrl= '<%# "WallPaperRecord.aspx?id="+ Eval("Id") %>'

Height="32px" Width="32px"/>

"imgbtndel" runat="server" CommandName="delete"

ImageUrl="~/img/delete.png" Height="32px" Width="32px"/>

protected void Page_Load(object sender, EventArgs e)
{
Int32 ID = Convert.ToInt32(Request.QueryString["Id"]);
if (ID == null || ID == 0)
{
}
else
{
editmode();
}
if (!IsPostBack)
{
bindUsingCategory(); //bind dropdown from database
bindCategory(); //bind gridview
}
}
public void bindUsingCategory() //bind dropdown from database
{
using (WallpaperEntities13 context = new WallpaperEntities13())
{
ddlWallCategry.DataSource = (from r in context.WallPaperCategries select new { CategoryName = r.CategoryName, Id = r.Id }).ToList();
ddlWallCategry.DataTextField = "CategoryName";
ddlWallCategry.DataValueField = "Id";
ddlWallCategry.DataBind();
ddlWallCategry.Items.Insert(0, new System.Web.UI.WebControls.ListItem());
}
}
private void bindCategory() //bind gridview
{
using (WallpaperEntities13 context = new WallpaperEntities13())
{
GridViewCategory.DataSource = context.WallpaperRecords.ToList();
GridViewCategory.DataBind();
}
}
protected void ddlWallCategry_SelectedIndexChanged(object sender, EventArgs e)
{
using (WallpaperEntities13 context = new WallpaperEntities13())
{
var Category = (from em in context.WallpaperRecords
where em.CategoryId == ddlWallCategry.SelectedValue
select new
{
em.Id,
em.CategoryName,
em.Thumbnail,
}).ToList();
ddlWallCategry.DataTextField = "CategoryName";
ddlWallCategry.DataValueField = "Id";
GridViewCategory.DataSource = Category;
GridViewCategory.DataBind();
}|
}
protected void editmode()
{
Int32 ID = Convert.ToInt32(Request.QueryString["CategoryName"]);
using (WallpaperEntities13 ctx = new WallpaperEntities13())
{
btnupdate.Visible = true;
btnSave.Visible = false ;
var Category = int.Parse(Request["Id"]);
var query = (from c in ctx.WallpaperRecords
where c.Id == Category
select new
{
c.CategoryName,
c.Id,
c.CategoryId,
c.Thumbnail
}).FirstOrDefault();
if (query != null)
{
lblCategoryName = query.CategoryName.ToString();
ddlWallCategry.SelectedValue = query.CategoryId;
ctx.SaveChanges();
GridViewCategory.EditIndex = -1;
ddlWallCategry. DataBind(); //getting error in this line...ddlWallCategry' has a SelectedValue which is invalid because it does not exist in the list of items.
}
ddlWallCategry.SelectedValue = "";
}
}
protected void btnupdate_Click(object sender, EventArgs e)
{
using (var context = new WallpaperEntities13())
{
var Categorys = int.Parse(Request["Id"]);
string Category = Convert.ToString(Session["CategoryName"]);
var std = (from x in context.WallpaperRecords
where x.CategoryName == Category
select x).FirstOrDefault();
if (std != null)
{
std.CategoryName = lblCategoryName.ToString();
context.SaveChanges();
GridViewCategory.EditIndex = -1;
DataBind();
}
}
}