Battles with sorting DataGrid control.

[ChrisM]

Can anyone please tell me what I'm doing wrong here.
I have a Windows Form with a DataGrid on it, and I'm having real problems
with the Sorting.

It is easy to reproduce the problem I have.

If you create a new Windows Application
Put a DataGrid control on it.

Put the following in the onload event of the form:

private void Form1_Load(object sender, System.EventArgs e)
{
DataGridTableStyle dgts = new DataGridTableStyle();
DataGridTextBoxColumn dgtbc1 = new DataGridTextBoxColumn();
DataGridTextBoxColumn dgtbc2 = new DataGridTextBoxColumn();

dgtbc1.Width = 300;
dgtbc1.HeaderText = "Header1";
dgts.GridColumnStyles.Add(dgtbc1);

dgtbc2.Width = 300;
dgtbc2.HeaderText = "Header2";
dgts.GridColumnStyles.Add(dgtbc2);

dataGrid1.TableStyles.Add(dgts);

DataTable dt = new DataTable("SuperTable");
dt.Columns.Add("One");
dt.Columns.Add("Two");

dataGrid1.DataSource = dt;
}

So by my understanding, I have created a tableStyle and added a couple of
textBoxColumns to it, then applied that style to my datagrid.
I have then created a DataTable, and made that the dataSource of my
dataTable.

If you run the app you should get an empty grid.

In Column1 put the letters a-h
In Column2 put the numbers 1-8
Click on the header of Column1 a couple of times so that the letters are
sorted a-h
Click on the 5 in Column2 and change it to 100.
Try clicking on the header of Column2 to sort the numbers correctly.
Why doesn't that work? The row with '100' in it stays in position, doesn't
get re-sorted.

Note: If you click on a few cells in the table, then it seems to sort itself
out,
but how can I re-produce that in code?

I'm sure that I've done somthing dumb, but I can't see it.
If anyone can cast light on this, I will be most grateful

Regards,

Chris.

 

[Nicholas Paldino [.NET/C# MVP]]

Chris,

When you type the 100, and then click the header of the grid, I noticed
that the edit mode does not change. This would indicate that the value
hasn't been written to the underlying data table yet, which would explain
why the sort doesn't occur. When you move off the cell, the value is
committed, and then the sort is applied correctly.

In order to commit the edit in code, you have to find the
BindingManagerBase for the data binding (you can pass the data table that
the grid is bound to to the BindingContext property of the data grid to get
the binding manager base). Once you have that, call EndCurrentEdit on the
BindingManagerBase, and the value should be committed to the data table, and
the sort applied.

Hope this helps.

 

[ChrisM]

Nicholas,

Thank You 1000 times!

I had guessed that it was probably somthing to do with the data not getting
written back to the DataTable (In fact a DataView of a DataTable) but I had
no idea how to force it through. I have seen BindingContext in other places,
but until now, I haven't really understood what it meant.

EndCurrentEdit works great, now my DataGrid does what I was expecting it to.
For anyone else with this problem:
dataGrid1.BindingContext[dataGrid1.DataSource].EndCurrentEdit();

In my actual app, values in the grid are being changed by code, rather than
being typed in, but I assume that the pricinple is similar. Your proposed
solution certainly seems to work for me anyway.

Once again thanks, you won't believe how crazy this has been driving me!

ChrisM

Chris,

When you type the 100, and then click the header of the grid, I noticed
that the edit mode does not change. This would indicate that the value
hasn't been written to the underlying data table yet, which would explain
why the sort doesn't occur. When you move off the cell, the value is
committed, and then the sort is applied correctly.

In order to commit the edit in code, you have to find the
BindingManagerBase for the data binding (you can pass the data table that
the grid is bound to to the BindingContext property of the data grid to get
the binding manager base). Once you have that, call EndCurrentEdit on the
BindingManagerBase, and the value should be committed to the data table, and
the sort applied.

Hope this helps.


--
- Nicholas Paldino [.NET/C# MVP]
- (e-mail address removed)

Can anyone please tell me what I'm doing wrong here.
I have a Windows Form with a DataGrid on it, and I'm having real problems
with the Sorting.

It is easy to reproduce the problem I have.

If you create a new Windows Application
Put a DataGrid control on it.

Put the following in the onload event of the form:

private void Form1_Load(object sender, System.EventArgs e)
{
DataGridTableStyle dgts = new DataGridTableStyle();
DataGridTextBoxColumn dgtbc1 = new DataGridTextBoxColumn();
DataGridTextBoxColumn dgtbc2 = new DataGridTextBoxColumn();

dgtbc1.Width = 300;
dgtbc1.HeaderText = "Header1";
dgts.GridColumnStyles.Add(dgtbc1);

dgtbc2.Width = 300;
dgtbc2.HeaderText = "Header2";
dgts.GridColumnStyles.Add(dgtbc2);

dataGrid1.TableStyles.Add(dgts);

DataTable dt = new DataTable("SuperTable");
dt.Columns.Add("One");
dt.Columns.Add("Two");

dataGrid1.DataSource = dt;
}

So by my understanding, I have created a tableStyle and added a couple of
textBoxColumns to it, then applied that style to my datagrid.
I have then created a DataTable, and made that the dataSource of my
dataTable.

If you run the app you should get an empty grid.

In Column1 put the letters a-h
In Column2 put the numbers 1-8
Click on the header of Column1 a couple of times so that the letters are
sorted a-h
Click on the 5 in Column2 and change it to 100.
Try clicking on the header of Column2 to sort the numbers correctly.
Why doesn't that work? The row with '100' in it stays in position, doesn't
get re-sorted.

Note: If you click on a few cells in the table, then it seems to sort itself
out,
but how can I re-produce that in code?

I'm sure that I've done somthing dumb, but I can't see it.
If anyone can cast light on this, I will be most grateful

Regards,

Chris.