Question

I have a following interface:

public interface IDataAccessor
    {
        IList GetAllRecords();
        IFormEditor ShowAddEditForm();


    }

and class which inheritance this interface:

 public class LanguageDataAccessor : IDataAccessor
    {

        public void SaveLanguage(Languages language)
        {
            LanguagesDAO languages = new LanguagesDAO();
            languages.Save(language);
        }
    // other methods...
}

In user control I have the following code:

public partial class ucDisplayDictionary : UserControl
    {
        public Type DictionaryName { get; set; }
        public IDataAccessor DataAccessor { get; set; } 

public ucDisplayDictionary(IDataAccessor accessor)
            : this()
        {
            DataAccessor = accessor;
            DictionaryName = accessor.GetType();
        }

private void btnEditRecord_Click(object sender, EventArgs e)
         {
             if (dgvDisplayDictionary.CurrentRow != null)
             {
                 var frmEdit = DataAccessor.ShowAddEditForm();

                 frmEdit.SetValue(dgvDisplayDictionary.CurrentRow.DataBoundItem);                    

                 if (frmEdit.GetForm().ShowDialog() == DialogResult.OK)
                 {
                     dgvDisplayDictionary.DataSource = null;
                     dgvDisplayDictionary.DataSource = ((LanguageDataAccessor)DataAccessor).Collection; // *                           
                 }
             }    
         }

In the string (*) I want to write something like that:

dgvDisplayDictionary.DataSource = ((DictionaryName)DataAccessor).Collection;

because this user control is common for other DataAccessor,

How can I do this?
Thanks and sorry for my english.

Answer 1

If all your IDataAccessor implementations have a Collection property, you should put that property in IDataAccessor – then you don’t need a cast at all.

If your Collection property is strongly typed, you might want something like:

public interface IDataAccessor
{
    IList GetAllRecords();
    IFormEditor ShowAddEditForm();
    IList Collection { get; }
}

public interface IDataAccessor<T> : IDataAccessor
{
    new IList<T> Collection { get; }
}

(In the same way as IEnumerator has the non-generic Current, and the generic IEnumerator<T> has the generic property.)

That way anything which needs the collection in a strongly typed way can use IDataAccessor<T> but you don’t need to make your ucDisplayDictionary class generic. (I suggest you rename that to follow .NET conventions by the way – it looks ghastly at the moment.)

It’s possible that your IDataAccessor.GetAllRecords() method already does what you want of course, and you only need to change your code to:

 dgvDisplayDictionary.DataSource = DataAccessor.GetAllRecords();

(You don’t need to set the DataSource to null first, by the way.)