Friday, November 13, 2009

Set default values of new generated rows at implementing filter

This is a simple trick to handle a common problem

Problem:
You provided a filter option for showing a list, you wanted user to add new items to list, and if list is filtered the new item should be added to the current filtered list.
Requirements:
1. You used the ICollectionView to bind the list, if you don’t do.
2. On of these
  • There is no item that doesn’t belong to any filter.
  • You have a way to recognize newly created objects.
Solution:

First see the below code, pay attention to comments

anICollectionView.Filter = o=>
    {
        var unit = o as Unit;
        if (unit.UnitCategory == null)
        {
            // This is a tricky code, there is 3 points: // 1. This code will be executed only if the list is shown in categorized mode // 2. All units have a unit category, so I didn't change any other unit's unit category // 3. Regarding to point 2 this unit which has no unit category is a new added unit, you bet! unit.UnitCategory = currentUnitCategoryOnFilter; // 4. So I can set the unit category of this newly created unit to the current filter }
        return unit.UnitCategory = currentUnitCategoryOnFilter);
    };

the line
if (unit.UnitCategory == null)
is the way that I recognize this a new object because all units have a unit category.

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