Dependency Injection in WinForms

Geni Lou

in Program.cs I add this code:

services.AddDbContext(context => context.UseSqlServer(constr));
services.AddScoped();
services.AddScoped();

in MDIForm I add this code:

private readonly IClassService classService;
private readonly ICategoryService categoryService;
public MdiForm(IClassificationService classificationService, ICategoryService categoryService){
this.classService = classService;
this.categoryService = categoryService;}

then to show a category from MDI I do this code. But in order to add the classService from CategoryForm to Classification, it should be a part of CategoryForm.

from MDI Form to show CategoryForm:

var categoryForm = new frmCategory(classService, categoryService);
categoryForm.ShowDialog();
from CategoryForm to show ClassForm:
var classForm = new frmClass(classService);
classForm .ShowDialog();

3 Replies

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Mario Scheeren5y ago
Accepted answer
Thought it would be obvious ....
public interface IFormsFactory
{
SubForm CreateSubForm();
}
internal class FormsFactory : IFormsFactory
{
}
Geni Lou5y ago
When I try the code below it shows

CS0246: tye type or namespace name "IFormsFactory' could not be found (are you missing a using directive or an assembly reference?)
IFormsFactory formsFactory;
public MdiForm(IFormsFactory formsFactory)
{
InitializeComponent();
}
Mario Scheeren5y ago
You might use a Factory for creating your forms ... this way the factory could Inject the needed dependencies.
IFormsFactory formsFactory;
MainForm(IFormsFactory formsFactory)
{
    _formsFactory = formsFactory;
}

/********  snip  *********/

internal class FormsFactory
{
  readonly IDependantA _dependantA;
  public FormsFactory(IDependantA dependantA)
  {
     _dependantA = dependantA;
  }
  public SubForm CreateSubForm()
  {
    return new Subform(_depandantA);
  }
}

/********  snip  *********/

SubForm subForm = _formsFactory.CreateSubForm();
subForm.ShowDialog(this);