GridViewUpdateEventArgs.NewValues.Count = 0 ? 1

jmeckley · Aug 1, 2007

I'm experimenting with a GridViewXEventArgs. When Updating/Deleting the Keys and Values collection are empty. I can't figure out why.

here is a simple setup I created to reproduce my problem.
ASPX

Code:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="HardwareInventory.WebForm1" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "[URL unfurl="true"]http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">[/URL]

<html xmlns="[URL unfurl="true"]http://www.w3.org/1999/xhtml"[/URL] >
<head runat="server">
    <title>Untitled Page</title>
</head>
<body>
    <form id="form1" runat="server">
        <asp:GridView ID="MyGridView" runat="server" AutoGenerateColumns="false" DataKeyNames="Id">
            <Columns>
                <asp:BoundField HeaderText="Full Name" DataField="Name" />
                <asp:BoundField HeaderText="DOB" DataField="BirthDate" HtmlEncode="false" DataFormatString="{0:D}" />
                <asp:CommandField ButtonType="button" ShowEditButton="true" ShowDeleteButton="true" />
            </Columns>
        </asp:GridView>
    </form>
</body>
</html>

Code Behind

Code:

using System;
using System.Collections.Generic;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace HardwareInventory
{
    public partial class WebForm1 : Page
    {
        private List<Person> data
        {
            get
            {
                List<Person> toReturn = (List<Person>)ViewState["data"];
                if (toReturn == null)
                {
                    toReturn = new List<Person>();
                    toReturn.Add(new Person(1, "John", new DateTime(1950, 1, 1)));
                    toReturn.Add(new Person(2, "Jane", new DateTime(1960, 2, 2)));
                    toReturn.Add(new Person(3, "Mary", new DateTime(1970, 3, 3)));
                }
                return toReturn;
            }
        }

        protected override void OnInit(EventArgs e)
        {
            base.OnInit(e);

            this.MyGridView.RowEditing += new GridViewEditEventHandler(MyGridView_RowEditing);
            this.MyGridView.RowUpdating += new GridViewUpdateEventHandler(MyGridView_RowUpdating);
            this.MyGridView.RowDeleting += new GridViewDeleteEventHandler(MyGridView_RowDeleting);
            this.MyGridView.RowCancelingEdit += new GridViewCancelEditEventHandler(MyGridView_RowCancelingEdit);

            if(!this.IsPostBack)
            {
                this.BindGrid();
            }
        }

        void MyGridView_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
        {
            this.MyGridView.EditIndex = -1;
            this.BindGrid();
        }

        void MyGridView_RowEditing(object sender, GridViewEditEventArgs e)
        {
            this.MyGridView.EditIndex = e.NewEditIndex;
            this.BindGrid();
        }

        void MyGridView_RowDeleting(object sender, GridViewDeleteEventArgs e)
        {
            int index = this.data.FindIndex(delegate(Person p) 
            { 
                return [COLOR=red]e.Keys["Id"][/color].Equals(p.Id); 
            });
            this.data.RemoveAt(index);
            this.BindGrid();
        }

        void MyGridView_RowUpdating(object sender, GridViewUpdateEventArgs e)
        {
            Person person = this.data.Find(delegate(Person p) 
            { 
                return [COLOR=red]e.Keys["Id"][/color].Equals(p.Id); 
            });
            person.Name = (string)[COLOR=red]e.NewValues["Name"][/color];
            person.BirthDate = (DateTime)[COLOR=red]e.NewValues["BirthDate"][/color];
            this.BindGrid();
        }

        private void BindGrid()
        {
            this.MyGridView.DataSource = data;
                this.MyGridView.DataBind();
        }
    }

    public class Person
    {
        private int id;
        private string name;
        private DateTime birthDate;

        public int Id { get { return this.id; } }
        public string Name
        {
            get { return this.name; }
            set { this.name = value; }
        }
        public DateTime BirthDate
        {
            get { return this.birthDate; }
            set { this.birthDate = value; }
        }
        public int Age { get { return DateTime.Today.Year - this.BirthDate.Year; } }

        public Person(int id, string name, DateTime birthDate)
        {
            this.id = id;
            this.name = name;
            this.birthDate = birthDate;
        }
    }
}

The red text is where the NullReferenceException is thrown because the Key/NewValue count is 0.

any ideas?

Jason Meckley
Programmer
Specialty Bakers, Inc.

ca8msm · Aug 1, 2007

It looks as though you can't use keys if you are using templates fields or if you are not using the built in data controls. I haven't had time to verify this but that seemed to be the case from reading this.

____________________________________________________________
Mark,
[URL unfurl="true"]http://aspnetlibrary.com[/url]

Need help finding an answer? Try the Search Facility or read FAQ222-2244.

jmeckley · Aug 1, 2007

I seems templatefields are ok to extact a value from if [tt]<%#Bind("MyProperty")[/tt] is used. This works until I attempt to dyanimcally load a DropDownList.

so this works (I added the food property to person to test dropdowns)

Code:

<asp:TemplateField HeaderText="Favorite Food" SortExpression="Food">
    <EditItemTemplate>
        <asp:DropDownList ID="FoodDropDownList" runat="server" SelectedValue='<%# Bind("Food") %>'>
            <asp:ListItem Text="[ Select ]" Value="" />
            <asp:ListItem Text="Apple" Value="Apple" />
            <asp:ListItem Text="Avacado" Value="Avacado" />
            <asp:ListItem Text="Bananna" Value="Bananna" />
            <asp:ListItem Text="Mango" Value="Mango" />
            <asp:ListItem Text="Orange" Value="Orange" />
        </asp:DropDownList>
    </EditItemTemplate>
    <ItemTemplate><%# Eval("Food") %></ItemTemplate>
</asp:TemplateField>

but this does not work. No excpetions but it cannot find the bound value because I assign the value dynamically.

Code:

<asp:TemplateField HeaderText="Favorite Food" SortExpression="Food">
    <EditItemTemplate>
        <asp:DropDownList ID="FoodDropDownList" runat="server">
            <asp:ListItem Text="[ Select ]" Value="" />
        </asp:DropDownList>
    </EditItemTemplate>
    <ItemTemplate><%# Eval("Food") %></ItemTemplate>
</asp:TemplateField>

private readonly string[] food = new string[] { "Apple", "Bananna", "Orange", "Mango", "Avacado" };

private void MyGridView_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowIndex != -1 && e.Row.RowState == DataControlRowState.Edit)
    {
        Person p = (Person)e.Row.DataItem;

        DropDownList ddl = (DropDownList)e.Row.FindControl("FoodDropDownList");
        foreach (string food in this.food)
        {
            ddl.Items.Add(new ListItem(food, food));
        }
        ddl.SelectedIndex = ddl.Items.IndexOf(new ListItem(p.Food, p.Food));
    }
}

this throws an exception because it's trying to assign the selected value before the list of options is loaded

Code:

<asp:TemplateField HeaderText="Favorite Food" SortExpression="Food">
    <EditItemTemplate>
        <asp:DropDownList ID="FoodDropDownList" runat="server" SelectedValue='<%#Bind("Food") %>'>
            <asp:ListItem Text="[ Select ]" Value="" />
        </asp:DropDownList>
    </EditItemTemplate>
    <ItemTemplate><%# Eval("Food") %></ItemTemplate>
</asp:TemplateField>

private readonly string[] food = new string[] { "Apple", "Bananna", "Orange", "Mango", "Avacado" };

private void MyGridView_RowDataBound(object sender, GridViewRowEventArgs e)
{
    if (e.Row.RowIndex != -1 && e.Row.RowState == DataControlRowState.Edit)
    {
        DropDownList ddl = (DropDownList)e.Row.FindControl("FoodDropDownList");
        foreach (string food in this.food)
        {
            ddl.Items.Add(new ListItem(food, food));
        }
    }
}

Jason Meckley
Programmer
Specialty Bakers, Inc.

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GridViewUpdateEventArgs.NewValues.Count = 0 ? 1

jmeckley

Programmer

ca8msm

Programmer

jmeckley

Programmer

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