DataGridView not showing anything using LINQ setup - why?

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Hi Folks,

In my current project I'm using LINQ to SQL with an SQLite database, using VS2008 and c#. I wanted a form to display the contents of a table, so set up a DataGridView to do that. Unfortunately I can't get anything displayed - the DGV remains blank.

All the articles I've seen suggest the following should work, though it can also be done with a BindingSource:

C#

db = new RWInfoDB(dbConnection);
var rwInfoTableQuery = from d in db.GetTable<RWInfoTable>() orderby d.Id select d;
pkgView.Show();
int c = rwInfoTableQuery.Count();
pkgView.dataGrid.DataSource = rwInfoTableQuery;

Where RWInfoDB is my DataContext-derived class, dbConnection returns a pre-canned SQLite connection object, pkgView is the form the DGV is on, and the "int c" line just proves the query works.

Inspecting the DGV object at runtime shows a DataSource member with visible data - I can see the rows in there - and yet the DGV has 0 in Columns and Rows - as if it hasn't even looked at the DataSource.

[I started with Show() called after setting DataSource, but moved it to see if that would help]

Edit: Are there properties in the DGV that could stop it working in this way?

Any thoughts?

Ruth

Posted 2-Jun-11 2:57am

Ruth Ivimey-Cook

Updated 2-Jun-11 10:55am

v3

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2 solutions

Solution 1

To read a table in LINQ you have a variety of options.

The simplest would be to drag the table into the DBML design and use the following code:

Using (Mydatacontext mydc = new Mydatacontext ())
{
    List<mytable> rows = mydc.mytableresults.tolist();
    mydatasource= rows;
}
</mytable>

Another option would be to create a stored procedure and read the results in the same way as above to populate your grid. this method works much better when your queries become more complex

Posted 3-Jun-11 3:49am

milenalukic

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Ruth Ivimey-Cook 7-Jun-11 19:28pm

Sorry I didn't respond straight away - stuff got in the way.
So far I'm trying to avoid the DBML style methods as it introduces yet another set of unknowns for me.

As far as I can tell from your code snippet, you are saying that the examples (including those by MS) need the ToList<>() function applied for the DataContext, rather than supplying the DataContext itself as the DataSource?

I was looking earlier at articles such as:
www.c-sharpcorner.com/.../dbindlinq.aspx

I've just tried again using a BindingSource. Create the object, assign my IOrderableQuery<> to it's data source, then assign the binding to the DGV's DataSource. Again, I can see after all this that the BindingSource object has opened the query and loaded the first record, quite correctly, but the DGV has no columns, no rows.

I next tried uncommenting all but essential (size etc) setup in the xx.Designer.cs file; makes no difference. I've checked that the AutoGenerateColumns is set true.

Very confusing.

Thanks, Ruth

milenalukic 8-Jun-11 8:05am

have a look in the DGV Tasks - the little black arrow on the topright of grid. Make sure the datasource is set and that the columns are included.

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Ruth Ivimey-Cook · Accepted Answer · 2011-06-07T13:38:00

Sorted it!

I discovered in the MS docs a "throwaway" comment that "you must use properties" - what for, it didn't say.

However, although several things in LINQ worked fine with a field-based class for my table row object (the one tagged [Table] with [Column]'s within it), DGV doesn't. Make automatic properties of all the fields and the DGV works.