Dynamic Food Menu in C#

C# is capable of being much more object-oriented than VS (the IDE) uses. VS is in many ways a bad example of object-oriented programming. For example for MFC in C++, VS emphasizes creation of derived classes for controls. The IDE for C# seems to have been designed by VB programmers; the properties box and the window for creating events is not object-oriented in the sense that first we place controls on the form then we generate event handlers as members of the form. I see nothing in the IDE to guide a beginner to the creation of a derived class for controls. I suppose that one thing that is lacking in the C# IDE is a way to interactively change the class for a control from the .Net class to a derived class. MFC subclasses controls and I assume that .Net does not. The MFC way requires a little more learning but the .Net way is easy to understand by people familiar with deriving classes and such.

The thing I did not explain in my post here is that if a class is derived from a control, then the derived class will be shown in the toolbox and then controls can be created using the derived class in the designer, eliminating the requirement to modify the designer.cs file. If I were to write an article, I would explain that.

@Sam: I love your implementation!!! Even though it involves a bit of work in this example I am pretty sure it would be worthwhile when there are a lot of forms involved. Great work!!!

First note that the form does not have any TextBoxes, CheckBoxes or DateTimePickers. Next note that you don't want to clear the Labels. So for this application you only want to reset the ComboBoxes. Let's assume however that you did want to reset all the controls as in your sample. Then the object-oriented solution would be to:

1. create an interface to do a reset
2. create classes that inherit from each of the control classes and the interface
3. edit the Form1.Designer.cs file so thet the controls use the new classes
4. modify the reset code

So for the first item the interface could be:

interface IReset
{
void Reset();
}

And the classes could be:

class TextBoxResetable : TextBox, IReset
{
public void Reset()
{
Text = "";
}
}

class ComboBoxResetable : ComboBox, IReset
{
public void Reset()
{
SelectedIndex = -1;
}
}

class CheckBoxResetable : CheckBox, IReset
{
public void Reset()
{
Checked = false;
}
}

class LabelResetable : Label, IReset
{
public void Reset()
{
Text = "";
}
}

class DateTimePickerResetable : DateTimePicker, IReset
{
public void Reset()
{
Text = "";
}
}

Don't forget to do step 3 above. Then the reset code could be:

foreach (Control ctrl in container.Controls)
{
IReset r = ctrl as IReset;
if (r != null)
r.Reset();
}

This forum's software still mangles source code and I am not sure I know how to post code that is not mangled so the attached zip file shows your code modified in the manner above.Note that this might look like too much work but the same technique could be used for many other things.

I haven't looked at the code in the .zip but, unless you're using some kind of 2-way data-binding between the combobox items and the labels' Text properties, then changing one will have no effect on the other.

Your addendum looks OK to me though you can make it slightly more efficient by changing all the 'if's after the first to 'else if's because there's no point examining further conditions once you've found the type of control:

       public void ClearControlValues(System.Windows.Forms.Control container)
      {
         try
         {
            foreach (Control ctrl in container.Controls)
            {
               if (ctrl.GetType() == typeof(TextBox))
                  ((TextBox)ctrl).Text = "";
               else if (ctrl.GetType() == typeof(ComboBox))
                  ((ComboBox)ctrl).SelectedIndex = -1;
               else if (ctrl.GetType() == typeof(CheckBox))
                  ((CheckBox)ctrl).Checked = false;
               else if (ctrl.GetType() == typeof(Label))
                  ((Label)ctrl).Text = "";
               else if (ctrl.GetType() == typeof(DateTimePicker))
                  ((DateTimePicker)ctrl).Text = "";
            }
         }
         catch (Exception ex)
         {
            MessageBox.Show(ex.ToString());
         }
      }

 

In this case, I mean for "clear" to reset all the combo-boxes back to no selection, and if necessary, clear the labels that display the totals. But would resetting the boxes automatically clear the labels since they react to them in the first place?

Okay, after sitting down for a few minutes, I actually finished it. My addendum though is this. What is wrong with the code for this clear function, or is it complete and just needs to be put into a button.

public void ClearControlValues(System.Windows.Forms.Control container)
      {
         try
         {
            foreach (Control ctrl in container.Controls)
            {
               if (ctrl.GetType() == typeof(TextBox))
                  ((TextBox)ctrl).Text = "";
               if (ctrl.GetType() == typeof(ComboBox))
                  ((ComboBox)ctrl).SelectedIndex = -1;
               if (ctrl.GetType() == typeof(CheckBox))
                  ((CheckBox)ctrl).Checked = false;
               if (ctrl.GetType() == typeof(Label))
                  ((Label)ctrl).Text = "";
               if (ctrl.GetType() == typeof(DateTimePicker))
                  ((DateTimePicker)ctrl).Text = "";
            }
         }
         catch (Exception ex)
         {
            MessageBox.Show(ex.ToString());
         }
      }