How set default text in combbox

Hi,

I have a datagrid table that consists of columns in each row. I wanted to set a default text in the combobox saying "Select", as in image1 but it does not seem to appear on the combobox and appears as in image2.

Below is the code i used on my xaml:

<ComboBox Margin="2" Text="Select" SelectedItem="{Binding SelTargetSheet, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" ItemsSource="{Binding TargetSheet, Mode=TwoWay}">
<ComboBox.Resources>
<SolidColorBrush x:Key="{x:Static SystemColors.HighlightBrushKey}" Color="Transparent"/>
<SolidColorBrush x:Key="{x:Static SystemColors.HighlightTextBrushKey}" Color="Transparent"/>
</ComboBox.Resources>
<ComboBox.ItemTemplate>
<DataTemplate>
<StackPanel Orientation="Horizontal">
<Image Source="{Binding TypeIcon}" Width="16" Height="16"></Image>
<Label Content="{Binding Type3Name}"/>
</StackPanel>
</DataTemplate>
</ComboBox.ItemTemplate>
</ComboBox>


I used Text="Select" but does not seem to work, are there any other solutions for this?

Thank you.