Java和参考资料(Java and references)

 在之前的评论中已经给出了答案。 说出来...... 
 
protected void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
    {
        txtSODate.Text = DateTime.Now.Date.ToString("dd/MM/yyyy");
        //--
        dtProductDet = new DataTable("dtProductDet");
        dtProductDet.Columns.Add("PID", typeof(int));
        dtProductDet.Columns.Add("PName", typeof(string));
        dtProductDet.Columns.Add("Quan", typeof(decimal));
        dtProductDet.Rows.Add(0,"",0);
        //--
        GridView1.DataSource = dtProductDet;
        GridView1.DataBind();
    }
}

protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
{
    switch (e.CommandName.ToUpper())
    {
        case "ADD":
            dtProductDet.Rows.Add(0, "", 0);
            break;
        case "DELETE":
            dtProductDet.Rows.RemoveAt(Convert.ToInt32(e.CommandArgument));
            break;
    }
    GridView1.DataBind();
}

I have got the solution.
 
The problem is, when i am editing value in DropDownList or in TextBox, its value is not saving back to DataTable which is bind with GridView and TextBox and DropDownList. There is no automatic way to do this, so we have to write manual code to save values back to DataTable.
 
When i asked the question add button was in GridViewColumn and it was command Column, now i have added a button in GridView Footer.
 
So when i click on "Add new row" button, page is posted back, at first page load event fires and then Button_Click event fires. I have add code on Page.Load event, if page is posted back then pick data from GridView and Save it to DataTable.
 
Nextly Button_click event fires, so a new row adds in DataTable and DataTable will assign in DataSource of GridView and DataBind method executes and re-generates GridView.
 
I have a DropDownList which is also bind to a different DataTable other than GridView, so that after DataBind() i have to select manually value in DropDownList as per saved in DataTable of GridView.
 
protected void Page_Load(object sender, EventArgs e)
{
    if (!Page.IsPostBack)
    {
        txtSODate.Text = DateTime.Now.Date.ToString("dd/MM/yyyy");
        //--
        dtProductDet = new DataTable("dtProductDet");
        dtProductDet.Columns.Add("PID", typeof(int));
        dtProductDet.Columns.Add("PName", typeof(string));
        dtProductDet.Columns.Add("Quan", typeof(decimal));
        dtProductDet.Rows.Add(0,"",0);
        //--
        SetGridViewSource();
    }
    else
    {
        DataTable dtPD = dtProductDet;
        DropDownList ddlProd = null;
        if (GridView1.Rows.Count > 0)
        {
            for (int i = 0; i < GridView1.Rows.Count; i++)
            {
                ddlProd = (DropDownList)GridView1.Rows[i].Cells[gvci_Prod].FindControl("ddlProduct");
                dtPD.Rows[i]["PID"] = Convert.ToInt32(ddlProd.SelectedItem.Value);
                dtPD.Rows[i]["PName"] = ddlProd.SelectedItem.Text;
                dtPD.Rows[i]["QUAN"] = ((TextBox)GridView1.Rows[i].Cells[gvci_Quan].FindControl("txtQuan")).Text;
            }
        }
        dtProductDet = dtPD;
    }
}


protected void btnAdd_Click(object sender, EventArgs e)
{
    dtProductDet.Rows.Add(0, "", 0);

    DataTable dtPDet = dtProductDet;
    GridView1.DataSource = dtPDet;
    GridView1.DataBind();


    DropDownList ddlProd = null;
    DataRow drFind = null;
    for (int i = 0; i < GridView1.Rows.Count; i++)
    {
        ddlProd = (DropDownList)GridView1.Rows[i].Cells[gvci_Prod].FindControl("ddlProduct");
        drFind = dtProductMaster.Rows.Find(dtPDet.Rows[i]["PID"]);
        if(drFind != null)
        {
            ddlProd.SelectedIndex = dtProductMaster.Rows.IndexOf(drFind);
        }
    }

}