Using a value in a SQLite column to get display name on submit.

I have a User table in my SQLite database that holds a single row of data that I am wanting to use to set variables throughout my app. This table gets rebuild every time a user logs in, just in case the account number changes in the API.

#region User class
public class User
    {
        [PrimaryKey, AutoIncrement]
        public int Id { get; set; }
        public string DisplayName { get; set; }
        public string AcctNumb { get; set; }
    }
#endregion

I am wanting to pull the DisplayName from the table to call into a JSON string once you click the submit button. Here is a stripped down version of my xaml:

    <ListView x:Name="peopleList" HasUnevenRows="true"
            Grid.Row="0">
        <ListView.ItemTemplate>
            <DataTemplate>
                <ViewCell Height="300">
                        <Grid>
                            <Grid.RowDefinitions>
                                <RowDefinition Height="Auto"/>
                            </Grid.RowDefinitions>
                            <StackLayout Padding="5">
                                <Label x:Name="UserDisplayName" Text="{Binding DisplayName}"/>
                            </StackLayout>
                        </Grid>
                </ViewCell>
            </DataTemplate>
        </ListView.ItemTemplate>
    </ListView>

    <Entry x:Name="newPerson"
        Grid.Row="1"
        Placeholder="Email"/>

    <Entry x:Name="password"
        Grid.Row="2"
        Placeholder="Password"/>

    <Button Text="Add Person"
        Grid.Row="3"
        Clicked="OnNewButtonClicked" />

    <Label x:Name="statusMessage"
        Grid.Row="4" />

The listView is populated at page initialize:

List people = App.UserDatabase.GetAllPeople();
peopleList.ItemsSource = people;

The UserDatabase just returns all data:

    #region Get All People
    public List<User> GetAllPeople()
    {
        try
        {
            return database.Table<User>().ToList();
        }
        catch (Exception ex)
        {
            StatusMessage = 1;
        }

        return new List<User>();
    }
    #endregion

Once the OnNewButtonClicked is clicked I am wanting to pull the listView DisplayName to put into the jsonObject.

 public async void OnNewButtonClicked(object sender, EventArgs args)
    {
        statusMessage.Text = "";
        var httpClient = new HttpClient();
        var jsonObject = new List<AddUser>();
        jsonObject.Add(new AddUser() { Email = newPerson.Text, Password = password.Text, CreatedBy =  UserDisplayName.Text}); //The UserDisplayName.Text is erroring.
        var json = JsonConvert.SerializeObject(jsonObject);
        HttpContent httpContent = new StringContent(json);
        httpContent.Headers.ContentType = new MediaTypeHeaderValue("application/json");
        var result = await httpClient.PostAsync(WebAPI, httpContent);
        statusMessage.Text = App.UserDatabase.StatusMessage;
    }

The UserDisplayName.Text shows not to exist in the current context. I need to add this user's display name when they add a user. How do I pull the value in the DisplayName column to populate this value automatically? Or is SQLite not the best way to go about this?

Any help on this is greatly appreciated!