error while editing in dropdownlist..for send dropdownlistvalue iam getting object not set to instance of an object

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XML

<table cellpadding="8" cellspacing="3"  >

<tr>
    <td>
        Category Name:
    </td>
    <td>
        <asp:DropDownList ID="DropDownList1" runat="server"
            onselectedindexchanged="DropDownList1_SelectedIndexChanged"
            AutoPostBack="true" Width="146px" ontextchanged="DropDownList1_TextChanged">
        </asp:DropDownList>

    </td>
</tr>
<tr>
<td>
    SubCategory Name:
</td>
<td>
    <asp:DropDownList ID="DropDownList2" runat="server"  Width="146px"
        AutoPostBack="true" onprerender="DropDownList2_PreRender"
        onselectedindexchanged="DropDownList2_SelectedIndexChanged"
        ontextchanged="DropDownList2_TextChanged">
    </asp:DropDownList>
</td>
</tr>
<tr>
<td>
    Level Name: /td>
<td>
    <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
</td>
</tr>

my c# code is:

C#

 protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            filldropdown();
           
            fillgrid();

            if (Request.QueryString["id"] != null)
            {
                Button1.Visible = false;
                Button2.Visible = true;
                edits();
            }
            else
            {
                Button2.Visible = false;
                Button1.Visible = true;
            }

           
        }


    }

    public void fillgrid()
    {
        onlineexam oe = new onlineexam();
        //DataTable dt = oe.getcasestudy();
        DataTable dt = oe.getlevel();
        if (dt.Rows.Count == 0)
        {

        }
        else
        {
            GridView1.DataSource = dt;
            GridView1.DataBind();
        }

    }
    public void edits()
    {
        onlineexam oe = new onlineexam();
        int id = Convert.ToInt32(Request.QueryString["id"].ToString());
     
        DataTable dt = oe.getlevelbyid(id);
       
           string fn= dt.Rows[0]["CategoryId"].ToString();
        string sn = dt.Rows[0]["CategoryName"].ToString(); 
        DropDownList1.SelectedItem.Text = fn;
/*error here* Object reference not set to an instance of an object*/ DropDownList2.SelectedItem.Text= sn;

       // for (int z = 0; z < DropDownList1.Items.Count; z++)
       // {
       // if (DropDownList1.Items[z].Text == fn)
       // {
       //     DropDownList1.Items[z].Selected = true;
       // }
       //}
        //for (int x = 0; x < DropDownList2.Items.Count; x++)
        //{
        //    if (DropDownList2.Items[x].Text == sn)
        //    {
        //        DropDownList2.Items[x].Selected = true;
        //    }
        //}
            TextBox1.Text = dt.Rows[0]["LevelName"].ToString();
    }


    public void filldropdown()
    {
        onlineexam oe = new onlineexam();
        DataTable dt = oe.getcategoryid();
        if (dt.Rows.Count == 0)
        {
        }
        else
        {
            DropDownList1.DataSource = dt;
            DropDownList1.DataTextField = dt.Columns["CategoryName"].ToString();
            DropDownList1.DataValueField = dt.Columns["Id"].ToString();
            DropDownList1.DataBind();
            DropDownList1.Items.Insert(0, "Select");
        }
    }
   
    protected void Button1_Click(object sender, EventArgs e)
    {
        string CategoryId = DropDownList1.SelectedItem.Text.ToString();
        string CategoryName = DropDownList2.SelectedItem.Text.ToString();
      //  string CategoryName = DropDownList3.SelectedItem.Text.ToString();
        string LevelName = TextBox1.Text;
        onlineexam oe = new onlineexam();
        oe.addlevel(CategoryId, CategoryName, LevelName);
        MessageBox msg = new MessageBox();
        msg.Show("Level Added Successfully");
        fillgrid();
        DropDownList2.Items.Clear();
        TextBox1.Text = "";
    }
    protected void GridView1_RowDeleting(object sender, GridViewDeleteEventArgs e)
    {
        int id = Convert.ToInt32(GridView1.DataKeys[e.RowIndex].Value);

        MessageBox msg = new MessageBox();
        onlineexam oe = new onlineexam();
        // oe.deletecasestudy(id);
        oe.deletelevel(id);


        msg.Show("Deleting Successfully");
        fillgrid();
        DropDownList1.SelectedItem.Text = "Select";
        DropDownList2.Items.Clear();
        TextBox1.Text = "";
    }
    protected void Button2_Click(object sender, EventArgs e)
    {
        int id = Convert.ToInt32(Request.QueryString["id"]);
        string CategoryId = DropDownList1.SelectedItem.Text.ToString();
        string CategoryName = DropDownList2.SelectedItem.Text.ToString(); ;
        //string CategoryName = DropDownList3.SelectedItem.Text.ToString();
        string LevelName = TextBox1.Text;
        onlineexam oe = new onlineexam();
        oe.updatelevel(id, CategoryId, CategoryName, LevelName);
        MessageBox msg = new MessageBox();
        msg.Show("Level Added Successfully");
    }

    protected void DropDownList1_SelectedIndexChanged(object sender, EventArgs e)
    {
    }

    public void filldropdown2(int CategoryId)
    {
        onlineexam oe = new onlineexam();
        DataTable dt = oe.getsubcategoryid(CategoryId);
        if (dt.Rows.Count == 0)
        {

            //DropDownList2.Items.Insert(0, "Select");
            DropDownList2.Items.Insert(0, "NULL");
        }
        else
        {
            DropDownList2.DataSource = dt;
           // DropDownList2.DataTextField = dt.Columns["CategoryName"].ToString();
            //string d = dt.Columns["CategoryName"].ToString();
            //DropDownList2.DataTextField = d;
            DropDownList2.DataValueField = dt.Columns["CategoryName"].ToString();
            DropDownList2.DataBind();
            DropDownList2.Items.Insert(0, "Select");
        }
    }

    protected void DropDownList2_SelectedIndexChanged(object sender, EventArgs e)
    {

    }
    protected void DropDownList1_TextChanged(object sender, EventArgs e)
    {
        DropDownList2.Items.Clear();
        TextBox1.Text = "";
        int CategoryId = Convert.ToInt32(DropDownList1.SelectedItem.Value);
        filldropdown2(CategoryId);
    }
    protected void DropDownList2_TextChanged(object sender, EventArgs e)
    {

    }
    protected void DropDownList2_PreRender(object sender, EventArgs e)
    {
        
    }
}

Posted 7-Aug-12 21:25pm

Member 7767311

Updated 7-Aug-12 21:31pm

_Amy

v2

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Comments

AshishChaudha 9-Aug-12 7:03am

Is this issue solved without any solution...I can't find anything in accepted Solution..

Sergey Alexandrovich Kryukov 26-Mar-13 23:35pm

Please stop posting non-answers as "solution". It can give you abuse reports which eventually may lead to cancellation of your CodeProject membership. And the fact you even self-accepted on formally is just outrageous, a sure way for a ban. And you also pretended that you are answering someone else's question. I hope you won't do it after this warning.

Comment on any posts, reply to available comments, or use "Improve question" (above).
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—SA

2 solutions

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_Amy · Answer 1 · 2012-08-07T21:34:00

Solution 1

Hi,
Instead of :

C#

DropDownList1.SelectedItem.Text = fn;
/*error here* Object reference not set to an instance of an object*/ DropDownList2.SelectedItem.Text= sn;

Use:

C#

DropDownList1.Text = fn;
/*error here* Object reference not set to an instance of an object*/ DropDownList2.Text= sn;

Because you are entering custom text so selected item property will be null at that time until and unless you select any item from the list.

--Amit

Posted 7-Aug-12 21:34pm

_Amy

Comments

Member 7767311 9-Aug-12 1:29am

its not working

_Amy 9-Aug-12 1:31am

What error you are getting after editing..??

Member 7767311 9-Aug-12 1:36am

no but its not selecting anything

AshishChaudha · Answer 2 · 2012-08-07T22:07:00

Solution 2

C#

DropDownList1.SelectedValue= fn;

/*error here* Object reference not set to an instance of an object*/

No need of this

C#

 string fn= dt.Rows[0]["CategoryId"].ToString();
 string sn = dt.Rows[0]["CategoryName"].ToString(); 
 DropDownList1.SelectedItem.Text = fn;

filldropdown2(fn);
DropDownList2.SelectedItem.Text= sn;

The selectedText of dropdown will be automatically get selected, because you are binding DropdownList before going to edit().

Thanks
Ashish

Posted 7-Aug-12 22:07pm

AshishChaudha

Updated 8-Aug-12 20:08pm

v2

Comments

Member 7767311 9-Aug-12 1:30am

i want to select in edit automatically two dropdownvalues wen i click edit in gridview

Member 7767311 9-Aug-12 1:30am

u r solution is not working

AshishChaudha 9-Aug-12 2:06am

Dear, While editing and filling values in cascaded Dropdownlist. first dropdownlist is automatically fill on load, but when you edit you have to first fill second dropdownlist respect to the first dropdownlist items, then select value of dropdownlist what you are retrieving from database.

AshishChaudha 9-Aug-12 2:09am

try my updated solution..