在ASP.NET中从gridview删除一行

Question

I wants to delete a row from a gridview .Here is my code

      //page load event  
      if(page.isPostback==false)  
      {  
        dataset ds=null;  
        ds=(dataset)Session["ds1"];  
        //session will contain dataset ds1 with data selected by user  
        if(ds!=null)  
        {  
          gvdetails.datasource=ds.Tables["Bus_Table"];  
          gvdetails.DataBind();  
       }  
     }

      protected void gvdetails_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
    DataSet ds = (DataSet)Session["ds1"];
    ds.Tables["Bus_Table"].Rows[e.RowIndex].Delete();
    ds.Tables["Bus_Table"].AcceptChanges();
    Session["ds1"] = ds;
    gvDetails.DataSource = ds.Tables["Bus_Table"];
    gvDetails.DataBind(); 
}

The code is working fine but when i try to click on the delete link. I get a runtime error in this line "ds.Tables["Bus_Table"].Rows[e.RowIndex].Delete();"

  error :Object reference not set to an instance of an object.NULLREFERENCEEXCEPTION was unhandled by the usercode.Use the "new " keyword to create an object instance

I can't figure out the problem. Please help

Answer 1

Either :

• Session["ds1"] doesn't exist (because your DataSet isn't in Session),
• the Session doesn't have that table, or
• you're referencing a bad RowIndex.

Because the code's all chained together, you have two options to find out which:

1. Hook up a debugger and check the values of ds , ds.Tables["Bus_Table"] and ds.Tables["Bus_Table"].Rows[e.RowIndex] , OR
2. Add null checks in your code and deploy.

Answer 2

You appear to be binding to the employee table:

gvdetails.datasource=ds.Tables["employee"];  

and deleting from the Bus_Table table:

ds.Tables["Bus_Table"].Rows[e.RowIndex].Delete(); 

That's not going to work, is it?

Answer 3

// THIS IS A EXAMPLE AND THOUGHT IT MIGHT HELP

protected void GridView1_RowDeleting(object sender, GridViewDeleteEventArgs e)
    {
            string EmployeeID = GridView1.DataKeys[e.RowIndex].Value.ToString();
            string Query = “delete Employee where Employee.EmployeeID = “ + EmployeeID;
            BindGridData(Query);
     }

private void BindGridData(string Query)
{
  string connectionstring  =        ConfigurationManager.ConnectionStrings["SampleConnectionString"].ConnectionString;

  using (SqlConnection conn = new SqlConnection(connectionstring))
  {
    conn.Open();
    using (SqlCommand comm = new SqlCommand(Query, conn))
    {
        SqlDataAdapter da = new SqlDataAdapter(comm);
        DataSet ds = new DataSet();
        da.Fill(ds);
        GridView1.DataSource = ds;
        GridView1.DataBind();
    }
  }

}

Hope i am clear now...