Am try to bind data uploaded in a gridview but I got this error "Object reference not set to an instance of an object." while uploading the file

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C#

protected void Page_Load(object sender, EventArgs e)
        {
            if (!IsPostBack == false)
            {

                SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=MinisanteDb;Integrated Security=True");
                SqlCommand com = new SqlCommand("select id,name,type,data from  uploadd where name=@name", con);
                com.Parameters.AddWithValue("name", GridView1.SelectedRow.Cells[1].Text);
                con.Open();
                //con.Close();
                SqlDataReader dr = com.ExecuteReader();
                if (dr.Read())
                {
                    Response.Clear();
                    Response.Buffer = true;
                    Response.ContentType = dr["type"].ToString();
                    Response.AddHeader("content-disposition", "attachment;filename=" + dr["name"].ToString());     // to open file prompt Box open or Save file         
                    Response.Charset = "";
                    Response.Cache.SetCacheability(HttpCacheability.NoCache);
                    Response.BinaryWrite((byte[])dr["data"]);
                    Response.End();
                    Page_Load(sender, e);
                }
            }

[edit]Code block added - OriginalGriff[/edit]

Posted 6-Mar-13 22:40pm

Gilbertinino

Updated 6-Mar-13 22:44pm

OriginalGriff

v2

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Orcun Iyigun 7-Mar-13 4:49am

You have a null value. Which line you are getting the exception? I think here: Response.ContentType = dr["type"].ToString();

Gilbertinino 7-Mar-13 7:41am

I have the exception on this line of code com.Parameters.AddWithValue("name", GridView1.SelectedRow.Cells[1].Text);

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OriginalGriff · Answer 1 · 2013-03-06T22:50:00

First off, you need an extra "@" in there:

C#

SqlCommand com = new SqlCommand("select id,name,type,data from  uploadd where name=@name", con);
com.Parameters.AddWithValue("name", GridView1.SelectedRow.Cells[1].Text);

Becomes:

C#

SqlCommand com = new SqlCommand("select id,name,type,data from  uploadd where name=@name", con);
com.Parameters.AddWithValue("@name", GridView1.SelectedRow.Cells[1].Text);

Otherwise the parameter is not linked up to the query properly.

You don't say which line gives you the error, but the fact that you don't get an SQL exception indiates that that it is the Parameters.AddWithValue line that is probably throwing the null reference: So check your SelectedRow paramater and make sure there is one - probably it is null, but it could also be that the Cells collection does not have sufficient cells - check the Count as well.

Two other things: Don't use constructs like:

if (!IsPostBack == false)

It is slow any awkward to read:

if (IsPostBack)

Is a lot easier.
And don't use "magic numbers" like "1" - use a constant instead so if it moves later it only has to be changed in one place.