Data Binding / MVVM with unknown (in advance) columns

[Tim]

I have seen a bunch of queries here about binding to Hashtables or Dictionaries.  My problem, much like others, is that I don't know in advance what the columns will be, and I get back a collection (rows) of Dictionary (column = key, value = cell) from a web service, rather than a collection of objects with properties.

Imagine a generic grid that displays election results.  The rows could be the year, and the columns could be the candidate names and the cells could be the number of votes.  Since I do not control the query itself, I need to be prepared to handle an arbitrary set of values.  Ideally I would like to say AutoGenerateColumns=True and ItemsSource={Binding SomeEnumerableCollectionOfDictionaries} so that there is no code-behind.  I want sorting and filtering.

Creating the columns by hand (in code) will also require creating the cells by hand, since I haven't got an object with properties to bind to, even if I can figure out the column names (from the keys) in advance.

Pointers or suggestions are most welcome.

Thanks,
Tim

[Vlad]

Hello Tim,

 Why not use our lightweight DataTable? Please check also this blog post. 

Greetings,
Vlad
the Telerik team

[Tim]

How does one go about binding to an

ObservableCollection<T> MyItemsSource

when you do not know what type T is?  Your blog example works, but it does not bind the GridView to an observable collection and it isn't very MVVC-like.

Thanks,
Tim

[Tim]

How does your example deal with ColumnName containing a . (period) character?

table.Columns.Add(new DataColumn() { ColumnName = "Files matching *",  DataType = typeof(MyCustomType) });

works, but

table.Columns.Add(new DataColumn() { ColumnName = "Files matching *.pdf",  DataType = typeof(MyCustomType) });

does not.  I have reduced it to the "." being the problem.  I am now stuck wondering what other restrictions there are on column/property names.  Consider filtering a file system and you can imagine that people might create filters named for the file patterns they filter - I.e., *.pdf, which cannot become a column header in this example.

Help!  I'm facing a deadline of today... with a few more days to fix bugs.

Thanks,
Tim

[Tim]

Additionally, sorting causes the app to die:

Unhandled Error in Silverlight Application Code: 4004 Category: ManagedRuntimeError Message: System.ArgumentException: Invalid property or field - 'pdf' for type: MyCustomType at Telerik.Windows.Data.Expressions.MemberAccessTokenExtensions.CreateMemberAccessExpression(IMemberAccessToken token, Expression instance) at Telerik.Windows.Data.Expressions.ExpressionFactory.MakeMemberAccess(Expression instance, String memberName) at Telerik.Windows.Data.Expressions.ExpressionFactory.MakeMemberAccess(Expression instance, String memberName, Boolean liftMemberAccessToNull) at
...

so it must be using the "." to look for properties...

Tim

[Tim]

Here is a "worst-case" scenario kind of program (changes to the example):

private string[] props = new string[]
                             {
                                 "ID",
                                 "ID ",
                                 "I D",
                                 "I D ",
                                 " I D ",
                                 ".",
                                 "..",
                                 "*",
                                 "**",
                                 "*.pdf",
                                 ".pdf",
                                 ".txt.pdf",
                             };

public Page()
{
    InitializeComponent();

    table = new DataTable();

    foreach (string prop in props)
    table.Columns.Add(new DataColumn() { ColumnName = prop, DataType = typeof(string) });

    for (var i = 0; i < 10; i++)
    {
        DataRow row = table.NewRow();
        UpdateRowValues(row, i);

        table.Rows.Add(row);
    }

    RadGridView1.ItemsSource = table;
}

private void UpdateRowValues(DataRow row, int i)
{
    foreach (string prop in props)
    {
        row[prop] = string.Format("{{{0}}} {{{1}}}", prop, i);
    }
}

Tim

[Tim]

I have worked around this by manufacturing unique property names and adding a translation layer to get back the invalid property names.

Tim

[Brian]

Is a fix expected anytime soon to allow column headers that start with a number OR periods (.) within column headers?  We have also run across this issue with other characters as well.  Seems like a bug to me.

[Vlad]

Hello,

You can check this blog post for more info about how to achieve the same with dynamic objects:
http://blogs.telerik.com/vladimirenchev/posts/11-09-28/dynamic-binding-for-your-silverlight-applications.aspx

All the best,
Vlad
the Telerik team