WPF Combobox binding issue with object

Question

I have found several example of wpf combobox binding but when trying to adapt it I don't get the expected results. What appears in the combobox instead of the value is this: CuttingProblemHelper.Models.ComboBoxPairs

Can please anyone help?

Example of data in the SQL table:

Id CutProbCategId Problem

1 1 Brins coupés

2 1 Brins grafignés

3 1 Fil non dégainé

What I try to acheive is having a key, value pair for each entry in the combobox from an sql table.

So I created a class to store key, value pair:

namespace CuttingProblemHelper.Models {

public class ComboBoxPairs
{
    public int _Key { get; set; }
    public string _Value { get; set; }

    public ComboBoxPairs(int _key, string _value)
    {
        _Key = _key;
        _Value = _value;
    }
} }

Next get the data from the table and add them to the object ComboBoxPairs

private void AddProblemCategtoCombobox(int categ)
    {
        // erase list
        cmbxProblem.ItemsSource = null;

        // get list
        DataRow[] CutProblemsRows = gediDataSet.CutProblems.Select("CutProbCategId= " + categ);
        // we have rows
        if (CutProblemsRows != null)
        {
            // initialize object ComboBoxPairs
            List<ComboBoxPairs> cbp = new List<ComboBoxPairs>();
            foreach (DataRow row in CutProblemsRows)
            {
                // add id and problem key, value pair
                cbp.Add(new ComboBoxPairs(int.Parse(row["Id"].ToString()), row["Problem"].ToString()));
            }
            // define properties of combobox
            cmbxProblem.DisplayMemberPath = "_Value";
            cmbxProblem.SelectedValuePath = "_Key";
            // bind comboboxpairs list
            cmbxProblem.ItemsSource = cbp.ToList(); 
        }
    }

Here's the XAML of the combobox and formatting of the display of items:

<ComboBox x:Name="cmbxProblem" Grid.Column="1" Margin="10,10,10,10" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" SelectionChanged="cmbxProblem_SelectionChanged" FontSize="40" ItemsSource="{Binding Collection}" Grid.ColumnSpan="2">
            <ComboBox.ItemContainerStyle>
                <Style TargetType="{x:Type ComboBoxItem}">
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate TargetType="{x:Type ComboBoxItem}">
                                <Label   Name="lbl" Content="{Binding}" ></Label>
                                <ControlTemplate.Triggers>
                                    <Trigger Property="IsHighlighted" Value="True">
                                        <Setter TargetName="lbl" Property="FontStyle" Value="Normal"></Setter>
                                        <Setter TargetName="lbl" Property="Background" Value="AliceBlue"></Setter>
                                    </Trigger>
                                    <Trigger Property="IsSelected" Value="True">
                                        <Setter TargetName="lbl" Property="FontStyle" Value="Italic"></Setter>
                                    </Trigger>
                                    <Trigger Property="IsSelected" Value="False">
                                        <Setter TargetName="lbl" Property="FontStyle" Value="Normal"></Setter>
                                    </Trigger>
                                </ControlTemplate.Triggers>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>
            </ComboBox.ItemContainerStyle>
        </ComboBox>

Thank you very much!

https://stackoverflow.com/questions/70309478/c-sharp-wpf-how-can-i-programatically-create-as-many-texblocks-as-needed-to Also this: `cmbxProblem.ItemsSource = cbp.ToList();` should be: `cmbxProblem.ItemsSource = cbp;` — Trevor, Dec 20 '21 at 21:12
Try the [DisplayMemberPath](https://learn.microsoft.com/en-us/dotnet/api/system.windows.controls.itemscontrol.displaymemberpath?view=windowsdesktop-6.0) property — nalka, Dec 21 '21 at 02:02
DisplayMemberPath has been added but it did nothing alone. Maybe some other thing is missing. I dropped the idea to use a class to store the key value pair and I used this instead: MyCollection = new ObservableCollection>(); But I still need help to show only the value as the items in the combox not the [Key, Value] as it is now. I don't know yet how to fix this issue. — Nico D, Dec 21 '21 at 14:53

Nico D · Answer 1 · 2021-12-21T14:57:04.680

I found a solution but the combobox does not only display the value but it displays the paired key and value. But when a value is selected it displays only the selected value. Anyone knows what to change to show only the value without the key?

See pictures to better understand.

Here's the solution I came up with after searching several combobox solutions: In the XAML

<ComboBox x:Name="cmbxProblem" Grid.Column="1" Margin="10,10,10,10" VerticalAlignment="Stretch" HorizontalAlignment="Stretch" SelectionChanged="cmbxProblem_SelectionChanged" FontSize="40" ItemsSource="{Binding MyCollection}" DisplayMemberPath="_Value" SelectedValuePath="_Key" Grid.ColumnSpan="2">
            <ComboBox.ItemContainerStyle>
                <Style TargetType="{x:Type ComboBoxItem}">
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate TargetType="{x:Type ComboBoxItem}">
                                <Label   Name="lbl" Content="{Binding}" ></Label>
                                <ControlTemplate.Triggers>
                                    <Trigger Property="IsHighlighted" Value="True">
                                        <Setter TargetName="lbl" Property="FontStyle" Value="Normal"></Setter>
                                        <Setter TargetName="lbl" Property="Background" Value="AliceBlue"></Setter>
                                    </Trigger>
                                    <Trigger Property="IsSelected" Value="True">
                                        <Setter TargetName="lbl" Property="FontStyle" Value="Italic"></Setter>
                                    </Trigger>
                                    <Trigger Property="IsSelected" Value="False">
                                        <Setter TargetName="lbl" Property="FontStyle" Value="Normal"></Setter>
                                    </Trigger>
                                </ControlTemplate.Triggers>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Style>
            </ComboBox.ItemContainerStyle>
        </ComboBox>

In the code behind:

 private void AddProblemCategtoCombobox(int categ)
    {
        // delete list
        cmbxProblem.ItemsSource = null;

        // get items for list
        DataRow[] CutProblemsRows = gediDataSet.CutProblems.Select("CutProbCategId= " + categ);
        // we have items
        if (CutProblemsRows != null)
        {
            // create collection
            MyCollection = new ObservableCollection<KeyValuePair<int, string>>();

            foreach (DataRow row in CutProblemsRows)
            {
                // fill collection with items
                MyCollection.Add(new KeyValuePair<int, string>(int.Parse(row["Id"].ToString()), row["Problem"].ToString()));
            }
            // define properties for the combobox
            cmbxProblem.DisplayMemberPath = "Value";
            cmbxProblem.SelectedValuePath = "Key";
            cmbxProblem.ItemsSource = MyCollection; 
        }
    }

WPF Combobox binding issue with object

1 Answers1