showing form containing interface as parameter to a constructor WPF

Question

I am trying to show main window after successful login.I used interface as parameter to constructor in main window. Now when I try showing main window, I get an error because I cannot pass interface as parameter to main window.I saw many posts like mine but I thought it is quite different from them.

This is my main window constructor:

public Home_Page(IGetAllItemClass clas)
        {
            InitializeComponent();
            _allClass = clas;
        }
        IGetAllItemClass _allClass;

My code in login Window from where I need to show main form:

 Home_Page h = new Home_Page();
 h.ShowDialog();

My app.xaml:

<Application x:Class="Cafe_WPF.App"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:local="clr-namespace:Cafe_WPF"
             Startup="App_Startup">
    <Application.Resources>
        <ResourceDictionary>
            <ResourceDictionary.MergedDictionaries>
                <ResourceDictionary Source="scroll_style.xaml" />
            </ResourceDictionary.MergedDictionaries>
        </ResourceDictionary>
    </Application.Resources>
</Application>

This is my App.cs :

public partial class App : Application
    {
        void App_Startup(object sender, StartupEventArgs e)
        {
            #region login_dependencies
            var container = new UnityContainer();
            container.RegisterType<IGetIP, get_ip_address>();
            container.RegisterType<IUserDetails, get_user_details>();
          container.RegisterType<IgetBusinessDetailsFromPosId, get_business_info_from_pos>();
            #endregion
            #region home_page_dependencies
            var home = new UnityContainer();
            container.RegisterType<IGetAllItemClass, get_all_item_class>();
            Home_Page hm = home.Resolve<Home_Page>();
            #endregion
            Login_Window lg = container.Resolve<Login_Window>();
            lg.ShowDialog();
        }
    }

This is my interface:

namespace Cafe_WPF.Interface
{
  public interface IGetAllItemClass
    {
        DataTable item_class(string business_info_id, string rvc_id);
    }
}

And my class service implementing interface is:

class get_all_item_class : IGetAllItemClass
{
    public DataTable item_class(string business_info_id, string rvc_id)
    {
        try
        {
            string sql = //query
            return CafePOS.Library.DataAccessLayer.Instance.ExecuteQuery(sql);

        }
        catch (Exception ex)
        {
            throw ex;
        }
    }
}

I am trying to use dependency injection.May be I am missing something. Can anyone help me on this ? I am stuck on this.

Answer 1

You need to pass the dependency with the constructor var home = new HomePage(myDependencyInterface); If you don't have that dependency instantiated within your login page then you have to resolve it with your Unity container first: var myDependencyInterface = container.Resolve<myDependencyInterface>();

Also as asked in the comments of your question, are you using Prism? Because if so you just need to use NavigateAsync(nameof(HomePage)); and Unity will inject the dependency