Ok I have seen to many post about this and nothing work for me, I just do not get it. I have a simple datagrid which i want to add rows, NOTE: this datagrid have no relation with database so everything has to be done datatable or arraylist whatever you want to help me.

Im going to post a few lines of what i have so far.

<asp:DataGrid ID="dgHistoric" runat="server" ShowFooter="true" AutoGenerateColumns="false" OnItemCommand="InsertSaveHist" >
                        <Columns>
                            <asp:TemplateColumn HeaderText="OSR">
                                <ItemTemplate>
                                    <asp:Label ID="txtHisOsr" runat="server" Width="25" Text='<% #DataBinder.Eval(Container.DataItem, "Opsheetrev").ToString() %>'></asp:Label>
                                </ItemTemplate>
                                <FooterTemplate>
                                    <asp:TextBox ID="txtFHisOsr" runat="server" Width="25"></asp:TextBox>
                                </FooterTemplate>
                            </asp:TemplateColumn>
                             <asp:TemplateColumn HeaderText="Eng Dwg Rev.">
                                <ItemTemplate>
                                    <asp:Label ID="txtHisEdr" runat="server" Width="25" Text='<% #DataBinder.Eval(Container.DataItem, "Engdwgrev").ToString() %>'></asp:Label>
                                </ItemTemplate>
                                <FooterTemplate>
                                    <asp:TextBox ID="txtFHisEdr" runat="server" Width="25"></asp:TextBox>
                                </FooterTemplate>
                            </asp:TemplateColumn>
 <asp:TemplateColumn>
                                <FooterTemplate>
                                    <asp:Button ID="btnAddHis" runat="server" Text="Add" CommandName="InsertHist" />
                                </FooterTemplate>
                            </asp:TemplateColumn>
                        </Columns>
                    </asp:DataGrid>

now in the load page function i have this because i want the first row blank.

DataTable dtOpe = new DataTable();
                DataSet dsComp = new DataSet();
       
                DataRow drOpe;
                dtOpe.Columns.Add("Opsheetrev");
                dtOpe.Columns.Add("Engdwgrev");
                drOpe = dtOpe.NewRow();
                drOpe[0] = "";
                drOpe[1] = "";
                dtOpe.Rows.Add(drOpe);
                dsComp.Tables.Add(dtOpe);
                dgHistoric.DataSource = dsComp;
                dgHistoric.DataBind();

and finally the insert function

DataSet dsComp = new DataSet();
                DataTable dt = (DataTable)dgHistoric.DataSource;
                
                DataRow dr = dt.NewRow();
                string osr = ((TextBox)e.Item.Cells[0].FindControl("txtFHisOsr")).Text;
                string edr = ((TextBox)e.Item.Cells[1].FindControl("txtFHisEdr")).Text;
             
                dr[0] = osr;
                dr[1] = edr;
                dt.Rows.Add(dr);
                dsComp.Tables.Add(dt);
                dgHistoric.DataSource = dt;
                dgHistoric.DataBind();

an error is generated in this point DataRow dr = dt.NewRow(); saying NullReferenceException was unhandled by user code.

thanks in advance for any help.

you are trying to cast dataset to datatable, my suggestion is to get rid of dataset object as you can set datatable object directly as a datasource, and try to do everything without using any datasets here.

try to change
dgHistoric.DataSource = dsComp;
to
dgHistoric.DataSource = dsComp.Tables[0];

if there is only a table in the dataset.

hope it help.

This post should moved to ASP.NET. Use Session or ViewState

Code of Page_load

if (IsPostBack == false)
        {
            DataTable dtOpe = new DataTable();
            DataSet dsComp = new DataSet();

            DataRow drOpe;
            dtOpe.Columns.Add("Opsheetrev");
            dtOpe.Columns.Add("Engdwgrev");
            drOpe = dtOpe.NewRow();
            drOpe[0] = "";
            drOpe[1] = "";
            dtOpe.Rows.Add(drOpe);
            dsComp.Tables.Add(dtOpe);
            dgHistoric.DataSource = dsComp.Tables[0];
            dgHistoric.DataBind();
            Session["dt"] = dtOpe;
        }

Code of Insert Method

DataTable dt = (DataTable)Session["dt"];
        DataRow dr = dt.NewRow();
        string osr = ((TextBox)e.Item.Cells[0].FindControl("txtFHisOsr")).Text;
        string edr = ((TextBox)e.Item.Cells[1].FindControl("txtFHisEdr")).Text;

        dr[0] = osr;
        dr[1] = edr;
        dt.Rows.Add(dr);
         
        dgHistoric.DataSource = dt;
        dgHistoric.DataBind();

I tried the first two suggestions but got the same error, the third one adatapost resolved my issue thanks all.

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