Wpf Mvvm make an instance of NewCategory when createing a new Category

Question

Hi,
I have a window/usercontrol, where I want to make a new Category. So I have some controls (textbox, checkbox and so on), when writing in the first textcontrol, I want to make an instance of a NewCategory in the viewmodel, so when clicking on the save button I can save that instance NewCategory.

My problem is it doesn't make a instance of NewCategory.I go into the saveChangesNew but the NewCategory is still null.

What I'm doing wrong?

Best regards
Simsen :-)

My ViewModel
using System.Collections.Generic;
using Model.Account;
using DAL.Account;
using System.Linq;
using Model.Projects;
using DAL.Projects;
using System.ComponentModel;
using System.Windows.Input;

namespace ViewModel.Account
{
    public class CategoryViewModel
    {
        public CategoryViewModel()
        {
            LoadCategories();
            LoadProjects();
            CmdReset = new MyICommand(ResetFields);
            CmdSave = new MyICommand(SaveChanges);
            CmdSaveNew = new MyICommand(SaveChangesNew);
        }

        #region New
        public MyICommand CmdReset { get; set; }
        private void ResetFields()
        {
            SelectedCategory.CategoryId = 0;
        }
        #endregion

        #region Get
        public List Categories_GetAll { get; set; }
        public List Categories_GetActive { get; set; }
        public List Categories_GetInactive { get; set; }

        public void LoadCategories()
        {
            DalCategory dalCategory = new DalCategory();
            var categories = dalCategory.GetCategories();

            if (categories != null)
            {
                //All
                Categories_GetAll = categories;

                //Active
                Categories_GetActive = categories.Where(x => x.CategoryIsObsolete == false).ToList();

                //Inactive
                Categories_GetInactive = categories.Where(x => x.CategoryIsObsolete == true).ToList();
            }
        }

        public List Projects_GetActive { get; set; }

        public void LoadProjects()
        {
            DalProjects dalProjects = new DalProjects();
            var projects = dalProjects.GetProjects();

            if (projects != null)
            {
                //Active
                Projects_GetActive = projects.Where(x => x.ProjectIsActive == true).ToList();
            }
        }
        #endregion

        #region Set
        public MyICommand CmdSave { get; set; }
        public void SaveChanges()
        {
            if (SelectedCategory != null)
            {
                if (SelectedCategory.CategoryId == 0)
                {
                    //Ny
                    string test = SelectedCategory.CategoryName;
                }
                else
                {
                    //Ret
                    string test = SelectedCategory.CategoryName;
                }
            }
            if (NewCategory != null)
            {
                string test = "ok";
            }
        }

        public MyICommand CmdSaveNew { get; set; }
        public void SaveChangesNew()
        {
            if (NewCategory != null)
            {
                string test = "ok";
            }
        }
        #endregion

        #region Delete
        public MyICommand DeleteCommand { get; set; }
        private void OnDelete()
        {
            Category cat = SelectedCategory;
            int id = cat.CategoryId;
            int pid = cat.ProjectId;
            string projectName = cat.ProjectName;
            int projectId = cat.ProjectId;
            string catname = cat.CategoryName;
            bool catGlobal = cat.CategoryIsGlobal;
            bool catActive = cat.CategoryIsObsolete;
            string test = "";
            //Categories_GetActive.Remove(SelectedCategory);
        }

        private bool CanDelete()
        {
            return SelectedCategory != null;
        }
        #endregion

        #region SelectedItem
        private Category _newCategory;
        public Category NewCategory
        {
            get
            {
                return _newCategory;
            }

            set
            {
                _newCategory = value;
                OnPropertyChanged("NewCategory");
            }
        }

        private Category _selectedCategory;

        public Category SelectedCategory
        {
            get
            {
                return _selectedCategory;
            }

            set
            {
                _selectedCategory = value;
                OnPropertyChanged("SelectedCategory");
            }
        }
        #endregion

        #region INotifyPropertyChanged Members
        public event PropertyChangedEventHandler PropertyChanged;

        public void OnPropertyChanged(string propertyName)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }
        #endregion
    }
}

Accepted Answer

I give up. I make it instead reading each single value into the viewmodel

And get in the viewmodel with this

public string CategoryName { get; set; }

Answer

Hi Anja,
i would change the concept. In the ViewModel add a property CategoryView of the type Category and then bind the UI to this property. At the beginning a new instance is assigned and after each save a new instance is assigned again.

Classes:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Windows;
using System.Windows.Input;

namespace WpfApp040
{
  public class CategoryViewModel : INotifyPropertyChanged
  {
    public string Test { get; set; } = "VM test";
    public CategoryViewModel()
    {
      LoadCategories();
      LoadProjects();
      CmdReset = new MyICommand(ResetFields);
      CmdSave = new MyICommand(SaveChanges);
      CmdSaveNew = new MyICommand(SaveChangesNew);
    }

    #region New
    public MyICommand CmdReset { get; set; }
    private void ResetFields(object parameter) => CategoryView = new Category();
    #endregion

   #region new
    public MyICommand CmdSaveNew { get; set; }
    public void SaveChangesNew(object parameter)
    {
      // save new Category
      var x = CategoryView;
      ResetFields(null);
    }
    #endregion

    #region Get
    public List Categories_GetAll { get; set; }
    public List Categories_GetActive { get; set; }
    public List Categories_GetInactive { get; set; }

    public void LoadCategories()
    {
      DalCategory dalCategory = new DalCategory();
      var categories = dalCategory.GetCategories();

      if (categories != null)
      {
        //All
        Categories_GetAll = categories;

        //Active
        Categories_GetActive = categories.Where(x => x.CategoryIsObsolete == false).ToList();

        //Inactive
        Categories_GetInactive = categories.Where(x => x.CategoryIsObsolete == true).ToList();
      }
    }

    public List Projects_GetActive { get; set; }

    public void LoadProjects()
    {
      DalProjects dalProjects = new DalProjects();
      var projects = dalProjects.GetProjects();

      if (projects != null)
      {
        //Active
        Projects_GetActive = projects.Where(x => x.ProjectIsActive == true).ToList();
      }
    }
    #endregion

    #region Set
    public MyICommand CmdSave { get; set; }
    public void SaveChanges(object parameter)
    {
      if (SelectedCategory != null)
      {
        if (SelectedCategory.CategoryId == 0)
        {
          //Ny
          string test = SelectedCategory.CategoryName;
        }
        else
        {
          //Ret
          string test = SelectedCategory.CategoryName;
        }
      }
      //if (NewCategory != null)
      //{
      //  string test = "ok";
      //}
    }
    #endregion

    #region Delete
    public MyICommand DeleteCommand { get; set; }
    private void OnDelete()
    {
      Category cat = SelectedCategory;
      int id = cat.CategoryId;
      int pid = cat.ProjectId;
      string projectName = cat.ProjectName;
      int projectId = cat.ProjectId;
      string catname = cat.CategoryName;
      bool catGlobal = cat.CategoryIsGlobal;
      bool catActive = cat.CategoryIsObsolete;
      string test = "";
      //Categories_GetActive.Remove(SelectedCategory);
    }

    private bool CanDelete() => SelectedCategory != null;
    #endregion

    #region SelectedItem
    private Category _categoryView = new Category();
    public Category CategoryView
    {
      get => _categoryView;
      set
      {
        _categoryView = value;
        OnPropertyChanged(nameof(CategoryView));
      }
    }

    private Category _selectedCategory;

    public Category SelectedCategory
    {
      get => _selectedCategory;
      set
      {
        _selectedCategory = value;
        OnPropertyChanged("SelectedCategory");
      }
    }
    #endregion

    #region INotifyPropertyChanged Members
    public event PropertyChangedEventHandler PropertyChanged;
    public void OnPropertyChanged(string propertyName) =>
      PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
    #endregion
  }

  public class Category
  {
    public int CategoryId { get; set; }
    public int ProjectId { get; set; }
    public string ProjectName { get; set; }
    public string CategoryName { get; set; }
    public bool CategoryIsGlobal { get; set; }
    public bool CategoryIsObsolete { get; set; }
  }

  public class Project
  {
    public bool ProjectIsActive { get; set; }
  }

  internal class DalCategory
  {
    internal List GetCategories()
    {
      return new List();
    }
  }

  internal class DalProjects
  {
    internal List GetProjects()
    {
      return new List();
    }
  }

  public class MyICommand : ICommand
  {
    private readonly Predicate

Wpf Mvvm make an instance of NewCategory when createing a new Category

1 additional answer