updating a row in gridview

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writing this code on gridview_rowupdating event a error is comming object reference not set to instance of object.why?
my code is as follows:

C#

protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
    {
        GridViewRow row = GridView1.Rows[e.RowIndex];
        string constr = ConfigurationManager.ConnectionStrings["constr"].ToString();
        SqlConnection conn = new SqlConnection(constr);

        string id = (((Label)row.FindControl("lblid")).Text).ToString();

        string comments = (((TextBox)row.FindControl("txtcomments")).Text).ToString();
        conn.Open();
        SqlCommand CmdSql = new SqlCommand("Update leave set admin_comments='" + comments + "', granted='" + true + "' where id=" + id + " ", conn);
        CmdSql.ExecuteNonQuery();
        GridView1.EditIndex = -1;
        conn.Close();

Also it is not updating any row why?

Posted 5-Jun-13 22:04pm

Rambo_Raja

Updated 5-Jun-13 22:07pm

Sridhar Patnayak

v2

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ridoy 6-Jun-13 4:10am

do you check your database isn't null?

Rambo_Raja 6-Jun-13 4:14am

yes i hv checked it.its not null.

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Tadit Dash (ତଡିତ୍ କୁମାର ଦାଶ) · Answer 1 · 2013-06-05T22:26:00

Please debug your code and find out on which line you are getting that exception.

Some Points

This may throw exception, if there is no connection string names as "constr" in the web.config.

C#

string constr = ConfigurationManager.ConnectionStrings["constr"].ToString();

So, you should read it like below...

C#

if(ConfigurationManager.ConnectionStrings["constr"] != null 
    &&   
   !String.IsNullOrEmpty(Convert.ToString(ConfigurationManager.ConnectionStrings["constr"]))
  )
{
    string constr = ConfigurationManager.ConnectionStrings["constr"].ToString();
}

Extra .ToString() called, not necessary.

C#
```
string id = (((Label)row.FindControl("lblid")).Text).ToString();
```
Here .Text gives you a string, then why you again call .ToString(), which is not needed.
Here you are passing the id as a string. Please check what is the field type in Table.
Identity fields are mostly integer field, in that case it will throw exception.
Then you need to convert that id to integer and then pass in the query.

C#
```
SqlCommand CmdSql = new SqlCommand("Update leave set admin_comments='" + comments + "', granted='" + true + "' where id=" + id + " ", conn);
```