How can I set the default values in a ComboBox multicolumns?

Question

I have a multi columns combobox. After combo population, I try to set the default values, but I get this error message

Object reference not set to an instance of an object.

This my code

Property

public ObservableCollection<Model_Sedi> Sedi { get; set; }
private Model_Sedi _Sedi_Search;
public Model_Sedi Sedi_Search {
get { return _Sedi_Search; }
set {
    _Sedi_Search = value;
    OnPropertyChanged("Sedi_Search");
    }
    }

this is XAML

  <ComboBox x:Name="Cmb_Sede"                    
        ItemsSource="{Binding Sedi, Mode=TwoWay}"
                      SelectedValuePath="Value"
                      SelectedItem="{Binding Sedi_Search, Mode=TwoWay}" 

                      VerticalAlignment="Top" Width="189">
        <ComboBox.ItemTemplate>
            <DataTemplate>
                <StackPanel Orientation="Horizontal">
                    <TextBlock Text="{Binding IdSede, UpdateSourceTrigger=PropertyChanged}"></TextBlock>
                    <TextBlock Text="{Binding Sede, UpdateSourceTrigger=PropertyChanged}" Padding="10,0,0,0"></TextBlock>
                </StackPanel>
            </DataTemplate>
        </ComboBox.ItemTemplate>
        <ComboBox.Effect>
            <DropShadowEffect Color="#FF0A0A0A" Opacity="0.6"/>
        </ComboBox.Effect>
    </ComboBox>

Now, how can I set the default values ? (like this doesn't work)

Sedi_Search.Sede = "ABC"
Sedi_Search.IdSede = 111

Please don't yell IN ALL CAPS; this is a professional Q&A site, not kindergarten. Also, the word you're looking for is "default", spelled with a "t" at the end. — The Paramagnetic Croissant, Jan 17 '15 at 11:09

score 1 · Answer 1 · edited May 23 '17 at 12:21

1

You need to set the Sedi_Search property to a matching object from the Sedi collection. Just use LINQ for this:

Sedi_Search = Sedi.SingleOrDefault(x => x.Sede == "ABC" && x.InSede == 111);

Another way of writing this:

Func<Model_Sedi, bool> isMatch = delegate(Model_Sedi x)
{
    return x.Sede == "ABC" && x.InSede == 111;
};

Sedi_Search = Sedi.SingleOrDefault(isMatch);

The first version is just a shorthand version of the second. x is just a variable name used by the delegate/lambda expression. This SO question might prove useful: Linq and lambda expression.

edited May 23 '17 at 12:21

Community

1
1

answered Jan 16 '15 at 16:45

Steven Rands

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Hi Steven.. but wath's "x" ?? – Alan392 Jan 16 '15 at 17:07
`x` is just a variable name used by the lambda expression. See the edit to my answer for clarification. – Steven Rands Jan 19 '15 at 09:25

score 0 · Answer 2 · edited May 23 '17 at 11:58

0

Change SelectedValuePath="IdSede" in XAML and in View Model you have to do what Steven Rands is saying.

edited May 23 '17 at 11:58

Community

1
1

answered Jan 16 '15 at 17:10

Nikhil Agrawal

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I have change SelectedValuePath with "IdSede", using LINQ, but Sedi_Search is always Nothing – Alan392 Jan 16 '15 at 17:19
@Alan392: And do what Steven says. – Nikhil Agrawal Jan 16 '15 at 17:19

How can I set the default values in a ComboBox multicolumns?

2 Answers2