CODEWITHSUNDEEP
c#wpf
Master
Master

Reputation: 2153

Trouble adding to Database

So I currently have a Datagrid, When the notes in the Datagrid are selected, It populates the Textbox Fields. That part works completely. I want to implement an "AddNewNote Button" the issue I currently have is that if an item was never selected, I get a nullreference. If an item was selected before hitting the button it works! But I need it to work in both scenarios.

private NoteDTO selectedNote;
public NoteDTO SelectedNote
{
    get { return this.selectedNote; }
    set
    {
        if (this.selectedNote == value)
            return;            
        this.selectedNote = value;
        this.OnPropertyChanged("SelectedNote");
    }
}

xaml side

<DataGrid ItemsSource="{Binding Notes}" SelectedItem="{Binding SelectedNote}" />
<TextBox Text="{Binding SelectedNote.Subject}" />
<toolkit:RichTextBox Text="{Binding SelectedNote.Comments, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}" />

public void AddNewNote()
{
    var newNote = new Note();
    newNote.Person_Id = PersonId;
    newNote.Comments = SelectedNote.Comments;
    newNote.Subject = SelectedNote.Subject;
    using (var ctx = DB.Get())
    {
        ctx.Notes.Add(newNote);
        ctx.SaveChanges();
    }
    this.OnPropertyChanged("newNote");
}

Upvotes: 0

Views: 57

Answers (1)

Grant Winney
Grant Winney

Reputation: 66449

You're trying to bind to properties on SelectedNote, which is causes the exception when it's null:

<TextBox Text="{Binding SelectedNote.Subject}" />
<toolkit:RichTextBox Text="{Binding SelectedNote.Comments, ... }" />

You could handle this in the getter/setter, making sure that SelectedNote is never null:

get { return this.selectedNote ?? (this.selectedNote = new NoteDTO()); }
set
{
    if (this.selectedNote == value)
        return;            
    this.selectedNote = value ?? new NoteDTO();  // make sure it's never `null`
    this.OnPropertyChanged("SelectedNote");
}

Upvotes: 1

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