asked on

Adding and removing rows from a grid view in asp.net

___________________________Asp.net Code_________________________

<asp:Button runat="server" ID="AddColumn" Text="Add Details" OnClick="AddColumnDetails"/>
<asp:Button runat="server" ID="removeHeaderentry" Text="Remove Entry" OnClick="RemoveHeaderEntry"/>

_________________________C# Code _____________________________

public partial class Generate_CCR_Rule : System.Web.UI.Page
{
DataTable DT1 = new DataTable();
DataRow DR1;

protected void Page_Load(object sender, EventArgs e)
{
//DT1 is the Data source for the Gridview CCRHeaderDetails

DT1.Columns.Add(new DataColumn("Column Name", typeof(string)));
DT1.Columns.Add(new DataColumn("CCR Header Rule Entry", typeof(string)));
CCRHeaderDetails.DataSource = DT1;
CCRHeaderDetails.DataBind();
}

protected void AddColumnDetails(object sender, EventArgs e)
{
DR1 = DT1.NewRow();
DR1["Column Name"] = "Some Text"
DR1["CCR Header Rule Entry"] = "Some Text";
DT1.Rows.Add(DR1);
CCRHeaderDetails.DataBind();

DR1=null;
}

protected void RemoveHeaderEntry(object sender, EventArgs e)
{ // hdnHSelect is the hidden variable which has the index of selected row from CCRHeaderDetails
GridViewRow row = CCRHeaderDetails.Rows[int.Parse(hdnHSelect.Value)];
DataRow dr = (row.DataItem as DataRowView).Row;
DT1.Rows.Remove(dr);
CCRHeaderDetails.DataSource = DT1;
CCRHeaderDetails.DataBind();
}

I have 2 problems here,
Firstly, when I click on "Add Details" button, it overwrites the row in the grid view (CCRHeaderDetails) every single time instead of creating a new row and adding it to the grid view
Secondly, the code for "Remove Entry" button is not working.

Could someone please help?

John Claes

The issue is the folowing : You're always starting with a EMPTY DT1 because the Pages are STATELESS ;-)
So you must fill the DT before you can do something

so what must be changed to get this done :

protected void AddColumnDetails(object sender, EventArgs e)
{
DT1 = CCRHeaderDetails.DataSource;
DR1 = DT1.NewRow();
DR1["Column Name"] = "Some Text"
DR1["CCR Header Rule Entry"] = "Some Text";
DT1.Rows.Add(DR1);
CCRHeaderDetails.DataBind();
DR1=null;
}

protected void RemoveHeaderEntry(object sender, EventArgs e)
{
DT1 = CCRHeaderDetails.DataSource;
GridViewRow row = CCRHeaderDetails.SelectedRow;
DataRow dr = (row.DataItem as DataRowView).Row;
DT1.Rows.Remove(dr);
CCRHeaderDetails.DataSource = DT1;
CCRHeaderDetails.DataBind();
}

Tina_Bhole

ASKER

Hi,

Sorry, but the recommended change did not have any effect on the output. I am still not able to add new rows to the gridview. It is still overwriting every time.

I had to use
DT1 = (DataTable)CCRHeaderDetails.DataSource;
instead of
DT1 = CCRHeaderDetails.DataSource;

In the RemoveHeaderEntry procedure,
GridViewRow row = CCRHeaderDetails.Rows[int.Parse(hdnHSelect.Value)];
gives following error:

Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index

If I use GridViewRow row = CCRHeaderDetails.SelectedRow; instead of the above statement, the variable "row" stores null value and DT1.Rows.Remove(dr); statement gives error.

Nasir Razzaq

You have to store the datatable in the session and use that instead of CCRHeaderDetails.DataSource. Call the DataBind() after adding the row.

Tina_Bhole

ASKER

Hello,
Please bare with me as I am still learning ASP.net.
I did not understand this. I have declared the data table inside the class. So, if I am not wrong, it's scope should be local to the methods/ procedures used inside that class. So, how does DT1 become empty? and If I declare it within the AddcolumnDetails, it will declare it every time I add click on add button.

I am calling DataBind() everytime I add to/ remove from the GridView/ DT1.

Could you please explain?

Thanks.

John Claes

Tina ,

Because you're in a webPage (==> read stateless) every time you start an Event
the Page is created again on ServerSide.

so initialisation is called ==>
DataTable DT1 = new DataTable();

and after the event is executed the Page_Load is called to ensure you'll get a response that is a page to show in the browser.

So if the Page_OnLoad filles DT1 from the DataBase CodeCruiser has a point
If you don't want everything inside the DataBase until Confirmed by the user ==>
Please place everything inside the folowing If
If Not IsPostBack Then
end if

Why ?
Every Event Called is done by creating a PostBack
The PAge_Onload will then not Call the database and refill the DataGRid.

poor beggar

Tina_Bhole

ASKER

Ok. I have put everthing in one procedure now.

protected void AddColumnDetails(object sender, EventArgs e)
{
string S="some text";

DataTable DT1 = new DataTable();
DataRow DR1;
DT1.Columns.Add(new DataColumn("Column Name", typeof(string)));
DT1.Columns.Add(new DataColumn("CCR Header Rule Entry", typeof(string)));

DT1 = (DataTable)CCRHeaderDetails.DataSource;
DR1 = DT1.NewRow();
DR1["Column Name"] = CCRList.Rows[int.Parse(hdnListitem.Value)].Cells[0].Text;
DR1["CCR Header Rule Entry"] = S;
DT1.Rows.Add(DR1);

CCRHeaderDetails.DataSource = DT1;
CCRHeaderDetails.DataBind();

DT1 = null;
DR1 = null;
}

This gives me error at DR1=DT1.NewRow(); : "Object reference not set to an instance of an object".

Just wanted to check, how do I copy data from grid view to the data table. Should I be using a for loop to go through each grid view row.

ASKER CERTIFIED SOLUTION

Nasir Razzaq

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Tina_Bhole

ASKER

Thanks a lot, this has solved my problem.