Autocomplete box pops a default message when no item exist

I am using an autocomplete box which is binded to a list in code-behind. What i want is that when there is no item in the list, the autocomplete box should show a message "no seller exist".

Following is the xaml-code

<rm:AutoCompleteBox Name="sellerText" Grid.Column="0" Grid.Row="2" VerticalAlignment="Top" HorizontalAlignment="Left" Width="170" Margin="110,40,0,0" >
        <rm:AutoCompleteBox.SelectedItem>
            <Binding Source="{StaticResource insertTransaction}" Mode="TwoWay" UpdateSourceTrigger="Explicit" Path="Seller">
                <Binding.ValidationRules>
                    <ExceptionValidationRule/>
                </Binding.ValidationRules>
            </Binding>
        </rm:AutoCompleteBox.Se开发者_StackOverflow社区lectedItem>
    </rm:AutoCompleteBox>

Code-behind

public NewRecord()
    {
        InitializeComponent();
        List<string> ledgerList = new List<string>();
        ledgerList = DAL_LedgerNameList.LoadLedgers();
        sellerText.ItemsSource = ledgerList;
    }

You could just add this logic in your code behind

public NewRecord()
{
    InitializeComponent();
    List<string> ledgerList = new List<string>();
    ledgerList = DAL_LedgerNameList.LoadLedgers();
    if (ledgerList.Length==0) 
    {
        sellerText.ItemsSource = new string() {"No Sellers Exist"}
    }
    else
    {
        sellerText.ItemsSource = ledgerList;
    }
}