C# FORM: Binding DataGridView to List<T>

[dave18]

Hello all!

I found a solution to my original question, but there's still so much I don't understand about it, I thought I'd give this forum a try. At the very least, maybe it will help someone else who got stumped like I did.

It seems so simple... binding a DataGridView to a List<T>. These are the two general problems that I kept running into:

(1) When the data in the list updated, the data on the screen did not update.
(2) When I finally got data on the screen to update, if I clicked any part of the DataGridView, the following message box popped up: "An unhandled exception of type 'System.IndexOutOfRangeException' occurred in System.Windows.Forms.dll Additional information: Index -1 does not have a value."

Here is the code that I finally got to work. Note that this code is completely contrived. I just tried to make the simplest example binding a list to a DataGridView that I could think of. Also, I am using .NET 2.0.

    public partial class Form1 : Form
    {
        private class Customer
        {
            private String _first;
            private String _last;
 
            public Customer(String first, String last)
            {
                _first = first;
                _last = last;
            }
 
            public String first { get { return _first; } }
            public String last { get { return _last; } }
        }
        private BindingList<Customer> customerList;
        private int iCount;
 
        public Form1()
        {
            InitializeComponent();
            customerList = new BindingList<Customer>();
            iCount = 0;
            updateDataGridView1();
        }
 
        private void button1_Click(object sender, EventArgs e)
        {
            iCount++;
            customerList.Add(new Customer("First" + iCount.ToString(), "Last" + iCount.ToString()));
            updateDataGridView1();
        }
 
        private void updateDataGridView1()
        {
            dataGridView1.DataSource = null;
            dataGridView1.DataSource = customerList;
        }
    }
 

Of special note to anyone else having problems, this binding doesn't work unless your list class has some type "properties" member function:

public String first { get { return _first; } }
public String last { get { return _last; } }
 

Also, I had to make the following statements every time I updated the list:

dataGridView1.DataSource = null;
dataGridView1.DataSource = customerList;
 

In addition, I had to use a BindingList<T> instead of a List<T> for customerList:

private BindingList<Customer> customerList;
 

Finally, if I used a BindingSource between the list and the DataGridView, it made no difference at all. I had all the sample problems using the BindingSource, and if I use a BindingSource in the example above, it works fine.

So, I still have a few questions about this whole thing, but to start with, am I missing the obvious?! For instance, why can't I just bind a normal List<T> to a DataGridView and have the grid view update when the list updates? When I read examples on the web, they seem so simple... but they don't work! Also, what if your list class--"Customer" in my code--has more properties methods than you want to appear in the DataGridView? Is there any way to mask them out?

Thanks a lot for any help. This has really been kicking my butt the past couple of days. Also, thanks to the folks involved with this archived thread: http://www.thescripts.com/forum/thread443793.html

That gave me the clues I needed to get my last problem solved.

Thanks again, and hopefully I'll be "talking" with some of you soon! :)
dave

[dave18]

Hey all,

I forgot to ask another part of my question. If I want the columns labeled "First Name" and "Last Name", I have to make the calls to update HeaderText each and every time I update the DataSource, as follows:

private void updateDataGridView1()
{
    dataGridView1.DataSource = null;
    dataGridView1.DataSource = customerList;
    dataGridView1.Columns["first"].HeaderText = "First Name";
    dataGridView1.Columns["last"].HeaderText = "Last Name";
}
 

That also seems strange to me.. I would think I should be able to do that just once, but then again l really suspect that I'm missing something very basic with this whole thing.

Thanks again for any help!
dave

[dave18]

OK, I think I've finally got this thing figured out. This is just in case anyone having trouble like I was finds this thread.

First of all, a List<T> will work, but a "better" solution is to use something like a DataTable and use that as the DataSource for your DataGridView. With that DataTable, column sorting will be implemented, for instance.

Second of all, and this is a big one, whether you use a List<T> or a DataTable, after you assign your DataSource to your DataGridView, make sure that the AutoGenerateColumns property is false:

dataGridView1.AutoGenerateColumns = false;
 

Without that, the DataGridView doesn't get updated by itself. Furthermore, without that, when it does get updated, all its values get reset. It seems so simple looking at it now, but without that, this isn't very fun.

Anyhow, I hope that helps someone. It took a while to get the hang of this, but now I've got a sweet DataGridView displaying my data. It handles sorting and everything.

Good luck to those wrestling with this one! :)
dave

[chylld]

hi dave,

i'd just like to say that your 3 posts helped me a tremendous amount. i too had been suffering similar pains with datagridviews; no matter how simple some other tutorials on the internet made it sound, the stupid things just refused to update!!

for me the critical thing that was wrong was that i was using a bindinglist<> between my datagridview and my list<>; once i fixed this it worked!!

my solution varies from yours a bit. what i've done is create a class that extends BindingList<> and i use that as my list of objects. this gets assigned directly as the datagridview's datasource. doing it this way allowed me to use the IDE to use this class as the datasource which allows me to adjust/hide columns in the IDE rather than in code :) also i don't need to set it to null or force any updates... i just edit the list and the datagridview updates itself (never thought i'd be able to say that)

[izitso]

Hi,

I've been wrestling with the same DataGridView problem that you mentioned for the last two days. Pretty new to C# but have a big project to finish.

I think we are missing part of the picture here, or at least I am - regarding events and threading scope. It's alluded to in a similar post but I didn't quite get the whole gist:

.NET Questions - (C#) updating DataGridView with a new DataSource

Turning autogenerate off didn't work for me. However that may be because I just instantiate a new datagridview object on the fly and attempt to set its datasource within the button click event of an existing form.

Help!

[hugoluis]

Hi to all,

I'm using List<T> objects to binding and i can't sort by any column, and also, i'd like to now how to manipute the order when before the columns are displayed

[djamwal]

Thanks a lot for your help, BindingList is exactly what was needed.

[TheCaptain]

For anyone else still struggling out there, I thought I'd make a comment in response to:
"(2) When I finally got data on the screen to update, if I clicked any part of the DataGridView, the following message box popped up: "An unhandled exception of type 'System.IndexOutOfRangeException' occurred in System.Windows.Forms.dll Additional information: Index -1 does not have a value.""

I started having this same exact problem when I tweaked my code some and after studying what changes brought about the error I believe that it has to do with assigning your DataGridView.DataSource to an empty List. As long as you make sure that that doesn't happen, you should be fine. Figured I'd share and maybe save somebody some frustration. Thanks for the post by the way, I found it helpful.

[John Thompson]

I have been harbouring a secret suspicion for some time now that Microsoft is staffed with people that are so intelligent that they don't even know that people that use their tools actually want to produce working solutions ASAP. The DataGridView is a calculated leap into the Stone Age from thie point of view. The question buzzing around in my mind is, what is the Microsoft’s grand plan, other than to loose out to Java. DataGridView is not the only area where Microsoft is making life harder for us.

[Frinavale]

John,

You typically chose your programming language based on the requirements of the application that you are developing. This means that there are situations where it is good to choose to use Java and other situations where .NET is the better choice.

Since you're posting in the C# forum, it is likely that many people here would tend to reply with ".NET is the better choice"...but it all depends on your requirements.

Anyways, the DataGridView is a control that is complicated and requires some learning to get used to it.

Microsoft is heading away from Win Form applications (where the DataGridView is used) and is pushing WPF (Windows Presentation Foundation) as the new technology to develop desktop (client) applications.

WPF does not have a DataGridView control.
It runs off of something called XAML...which is basically XML markup for specifying how your user interface is created. It is extremely flexible and very cool. (Definitely much "flashier" than Java)

You may think that the DataGridView is a difficult control to use (and you're right, new developers will have a hard time with it because it is complicated)....

But there are better (more complicated and exciting) things out there now (and have been for a long time!)

-Frinny

[NeCroFire]

Just to add more info on:
"(2) When I finally got data on the screen to update, if I clicked any part of the DataGridView, the following message box popped up: "An unhandled exception of type 'System.IndexOutOfRangeException' occurred in System.Windows.Forms.dll Additional information: Index -1 does not have a value."


I also set the DataSource of my DataGridView to List<T>. It's a list of contact numbers for a client. If I fill the list from the DB and display it, all is well. If you add a new client, the Contact number list is obviously empty. So now you add a new number to the List<T> in memory and update the Grid's display. Now if you click anywhere on the Grid it will throw the above exception.

If you already have a number in the DB and you just add another in memory to the List<T> and update the Grid's display... it works just fine.

It seems that when your List<> ONLY contains "memory" objects (Objects added in memory and none from the DB), the Grid throws the exception. I tried making sure that there are no NULL values anywhere in my List<> while working with "memory" objects, but it still threw the same exception every time.

Just to summarize:
- If your List contains one Number from the DB, you can add new numbers in memory to your List<> and the Grid would be fine.
- If you have zero numbers in you List<> from the DB and you add a new number in memory, the grid crashes with the above exception.

It makes ZERO sens and I spend all of last night trying to figure out why the Grid works fine with a List<> filled from the DB, but not when the List<> only has objects added in memory. What could possible be the difference??

Anyway, I'll try what was posted in the first 3 posts. I hope it will solve my problem.

Thanks

[NeCroFire]

Found a very good write up on how to properly use BindingList in the link below.
http://www.switchonthecode.com/tutor...o-a-collection


Also, I simply changed my List<> to a BindingList<> and now my grid seems to work perfectly.

Thanks again.