Question

When adding items to a gridview, I want the user to be able to select and edit/remove the item before writing the file (from the gridview entries) to a csv format. When I click on “edit” and update the information, I get an error. There is no row at position 0. (or whatever row you select to edit). Here is my code.

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        SetFocus(parttxtbox);
        table = new DataTable();
        MakeDataTable();
    }
    else
        table = (DataTable)ViewState["table"];

    ViewState["table"] = table;
}

protected void MakeDataTable()
{
    table.Columns.Add("Part", typeof(string));
    table.Columns.Add("Quantity", typeof(Int32));
    table.Columns.Add("Ship-To", typeof(string));
    table.Columns.Add("Requested Date", typeof(string));
    table.Columns.Add("Shipping Method", typeof(string));

    //Persist the table in the Session object.
    Session["table"] = table;

    //Bind data to the GridView control.
    BindData();
}

protected void addbtn_Click(object sender, EventArgs e)
{
    part = parttxtbox.Text.ToUpper();
    shipto = shiptotxtbox.Text;
    reqdate = reqdatecal.SelectedDate.ToShortDateString();
    shipmthd = shipddl.SelectedItem.ToString();
    CreateTable();
 }

public void CreateTable()
{
    DataRow row = table.NewRow();
    row["Part"] = part;
    row["Quantity"] = qty;
    row["Ship-To"] = shipto;
    row["Requested Date"] = reqdate;
    row["Shipping Method"] = shipmthd;
    table.Rows.Add(row);

    griditems.DataSource = table.DefaultView;
    griditems.DataBind();
}

private void BindData()
{
    griditems.DataSource = table;
    griditems.DataBind();
}

protected void griditems_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
    //Retrieve the table from the session object.
    DataTable dt = (DataTable)Session["table"];

    //Update the values.           
    GridViewRow row = griditems.Rows[e.RowIndex];
    dt.Rows[row.DataItemIndex]["Part"] = ((TextBox)(row.Cells[1].Controls[0])).Text;
    dt.Rows[row.DataItemIndex]["Quantity"] = ((TextBox)(row.Cells[2].Controls[0])).Text;
    dt.Rows[row.DataItemIndex]["Ship-To"] = ((TextBox)(row.Cells[3].Controls[0])).Text;
    dt.Rows[row.DataItemIndex]["Requested Date"] = ((TextBox)(row.Cells[4].Controls[0])).Text;
    dt.Rows[row.DataItemIndex]["Shipping Method"] = ((DropDownList)(row.Cells[5].Controls[0])).SelectedItem.ToString();


    //Reset the edit index.
    griditems.EditIndex = -1;
    //Bind data to the GridView control.
    BindData();

    ////Somewhat works, doesn't update the part field with the text entered
    //TextBox partedit = (TextBox)griditems.Rows[e.RowIndex].FindControl("Part");
    //DataRow row = table.NewRow();
    //row["Part"] = partedit;
    //row["Quantity"] = qty;
    //row["Ship-To"] = shipto;
    //row["Requested Date"] = reqdate;
    //row["Shipping Method"] = shipmthd;
    //table.Rows.Add(row);
}

The commented out part that says “Somewhat works” will write blanks in the field updated when you click update.

Answer 1

The time you are adding data table in Session there is no row in it, thats why you get error "There is no row at position 0."

You are assigning table from viewstate to table it would be session.

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        SetFocus(parttxtbox);
        table = new DataTable();
        MakeDataTable();
    }
    else
    if(Session["table"] != null)
        table = (DataTable)ViewState["table"];
}

protected void MakeDataTable()
{
    table.Columns.Add("Part", typeof(string));
    table.Columns.Add("Quantity", typeof(Int32));
    table.Columns.Add("Ship-To", typeof(string));
    table.Columns.Add("Requested Date", typeof(string));
    table.Columns.Add("Shipping Method", typeof(string));

    //Persist the table in the Session object.
    Session["table"] = table; //This adds table without any record in it. 

    //Bind data to the GridView control.
    BindData();
}

Add data table to session after you add records in datatable.

protected void addbtn_Click(object sender, EventArgs e)
{
    part = parttxtbox.Text.ToUpper();
    shipto = shiptotxtbox.Text;
    reqdate = reqdatecal.SelectedDate.ToShortDateString();
    shipmthd = shipddl.SelectedItem.ToString();
    CreateTable();
    Session["table"] = table;
 }

Update the Session[“table”] in griditems_RowUpdating after updating.

protected void griditems_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
    //Retrieve the table from the session object.
    DataTable dt = (DataTable)Session["table"];

    //Update the values.           
    GridViewRow row = griditems.Rows[e.RowIndex];
    dt.Rows[row.DataItemIndex]["Part"] = ((TextBox)(row.Cells[1].Controls[0])).Text;
    dt.Rows[row.DataItemIndex]["Quantity"] = ((TextBox)(row.Cells[2].Controls[0])).Text;
    dt.Rows[row.DataItemIndex]["Ship-To"] = ((TextBox)(row.Cells[3].Controls[0])).Text;
    dt.Rows[row.DataItemIndex]["Requested Date"] = ((TextBox)(row.Cells[4].Controls[0])).Text;
    dt.Rows[row.DataItemIndex]["Shipping Method"] = ((DropDownList)(row.Cells[5].Controls[0])).SelectedItem.ToString();


    //Reset the edit index.
    griditems.EditIndex = -1;
    //Bind data to the GridView control.
    BindData();

    Session["table"] = dt; 
}

Note: The way you are trying to get the updating recording is not appropriate you should read more about how to access data on row updating.