Treat control as either ComboBox or TextBox

Question

What is the best way to solve the following problem ?

foreach (Control control in this.Controls)
{
    if (control is ComboBox || control is TextBox)
    {
        ComboBox controlCombobox = control as ComboBox;
        TextBox controlTextbox = control as TextBox;

        AutoCompleteMode value = AutoCompleteMode.None;

        if (controlCombobox != null)
        {
            value = controlCombobox.AutoCompleteMode;
        }
        else if (controlTextbox != null)
        {
            value = controlTextbox.AutoCompleteMode;
        }

        // ...
    }
}

You see it's complicated enough to get the AutoCompleteMode-property. You can assume that it is guaranteed that I have either a ComboBox or a TextBox.

My first idea was to use generic with multiple types for T , but it seems that this is not possible in .NET:

public string GetAutoCompleteModeProperty<T>(T control) where T: ComboBox, TextBox // this does not work, of course

Sadly the both Controls don't have a common base class.

Note : This is meant to be a more general question used with a minimized example. In my case, I also want to access / manipulate other the AutoComplete*-proprties (which also both Controls have in common).

Thanks for ideas!

Answer 1

dynamic currentControl =  control;
string text = currentControl.WhatEver;

But, it throws an exception (Microsoft.CSharp.RuntimeBinder.RuntimeBinderException) if currentControl doesn't have WhatEver property

Answer 2

Depends on what you are trying to achieve. If you are just interested in the text property, then this is actually inherited from the Control class - therefore you don't need to cast the object. So you just need :

foreach (var control in this.Controls)
{
    value = control.Text;

    ...
}

If, however, you require more complicated logic, you should consider rethinking your control flow. I would suggest a View / Presenter model and handle each event individually - the approach of single responsibility can greatly reduce the complexity.

If you assign your view an interface with the expected properties - eg view.FirstName, view.HouseName or view.CountrySelection - that way the implementation (ie TextBox, ComboBox etc) is hidden. So :

public interface IMyView
{
    string FirstName { get; }
    string HouseName { get;}
    string CountrySelection { get; }
}

public class MyView : Form, IMyView
{
    public string FirstName { get { return this.FirstName.Text; } } // Textbox
    public string HouseName { get { return this.HouseName.Text; } } // Textbox
    public string CountrySelection { get { return this.CountryList.Text; } // Combobox
}

I hope that is of some assistance!

Answer 3

Use Type.GetType() . You just have to input a string representation of your property in.

if (sender is ComboBox || sender is TextBox)
{
  var type = Type.GetType(sender.GetType().AssemblyQualifiedName, false, true);
  var textValue = type.GetProperty("Text").GetValue(sender, null);
}

This also allows you to set the value of your properties too.

type.GetProperty("Text").SetValue(sender, "This is a test", null);

You could move this to a helper method to save rewriting code.

public void SetProperty(Type t, object sender, string property, object value)
{
  t.GetProperty(property).SetValue(sender, value, null);
}
public object GetPropertyValue(Type t, object sender, string property)
{
  t.GetProperty(property).GetValue(sender, null);
}

There is also room for exception handling by using this method.

var property = t.GetProperty("AutoCompleteMode");
if (property == null)
{
  //Do whatever you need to do
}