DisplayMemberPath concatenation

Unfortunately, this is not possible with DisplayMemberPath. You have the following alternatives:

• Specify a DataTemplate

  <ComboBox>
    <ComboBox.ItemTemplate>
      <DataTemplate>
        <TextBlock>
          <TextBlock.Text>
            <MultiBinding StringFormat="{}{0}: {1}">
              <Binding Path="idregion"/>
              <Binding Path="description"/>
            </MultiBinding>
          </TextBlock.Text>
        </TextBlock>
      </DataTemplate>
    </ComboBox.ItemTemplate>
  </ComboBox>
  

  ^{(If you are wondering about the empty braces in the StringFormat attribute, see: What do the {} brackets mean in the StringFormat section of a Binding syntax?)}

• Add a property or field to your data source. How to do that depends on your data source:

  If your combo box is bound to a DataTable, add a DataColumn and fill its values in a loop. Alternatively, change your SQL and add the concatenated value to your SELECT clause.

  If your combo box is bound to a POCO or entity framework object, add a property that returns the concatenation.

You need to use a DataTemplate:

<ComboBox Name="cboRegion">
    <ComboBox.ItemTemplate>
        <DataTemplate>
            <TextBlock>
                <Run Text="{Binding idregion}" />
                <Run Text="{Binding description}" />
            </TextBlock>
        </DataTemplate>
    </ComboBox.ItemTemplate>
</ComboBox>