ICollectionView Filter property - Null reference exception

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I am trying to use the filter property of ICollectionView object in WPF databinding. Code below -

C#

ICollectionView view = CollectionViewSource.GetDefaultView(GridProductInformation.DataContext);
int supplierID = GetComboBoxSelectedItem();
//Predicate<object> pred = new Predicate<object>(MatchSupplier);
Predicate<object> pred = delegate(object obj)
{
    NorthwindProduct _product = new NorthwindProduct();
    _product = obj as NorthwindProduct;
    int _supplierID = Convert.ToInt16(_product.SupplierID);
    if (_supplierID == supplierID)
        return true;
    else
        return false;
};
view.Filter(pred);

The code throwsa run time exception in the last line - Null reference exception. Object reference not set to instance of an object.

Any idea what is going wrong?

Posted 30-Sep-10 17:24pm

anshudutta

Updated 1-Oct-10 11:11am

Toli Cuturicu

v2

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Peter Neilson · Answer 1 · 2011-04-25T03:30:00

Solution 2

Apologies if you've found the answer already, but this if probably what you need ...

view.Filter = pred;

Posted 25-Apr-11 3:30am

Peter Neilson

Updated 25-Apr-11 3:41am

v2

PumbaPumba · Answer 2 · 2010-09-30T17:53:00

Solution 1

@anshudutta their is a casting problem itseems. Try setting a breakpoint at

_product = obj as NorthwindProduct;

I think this is always null.

Evaluate, what

obj

which is coming inside your predicate.

Posted 30-Sep-10 17:53pm

PumbaPumba

Comments

anshudutta 1-Oct-10 0:06am

I thought that initially, then I commented the code in my predicate and just wrote return True . It still throws the error.

PumbaPumba 1-Oct-10 0:09am

Do you got any samples for this to re-product. May be I'll give it a try.

anshudutta 1-Oct-10 0:21am

Well I am binding to a northwind database.. product table and trying to filter products by supplier ids. The combobox is bound to collection of supplier ids. When a particular supplier id is selected, the binding should filter products based on that supplier id. Cant understand why is it throwing Null exception