Can anyone explain what does this code mean?

Question

       [Description ("Foreground color"), Category ("Text Configuration")]
       property Color DrawColor
       {
          Color get()
          {
             return draw_color;
          }
          void set( Color val )
          {
             draw_color = val;
          }
       }

and also the below code and what's the difference between the above and below code?

    [Description ("Alignment to be used for this text"), Category ("Text Configuration")]
       [TypeConverter(AlignModeList::typeid)]
       property String ^ Alignment
       {
          String ^ get()
          {
             return alignment;
          }

          void set( String ^ val )
          {
             alignment = val;
          }
       }

public ref class AlignModeList : System::ComponentModel::StringConverter
   {
     public:
       static array<String ^> ^ alignmode = gcnew array<String ^>(3){"Left", "Centre", "Right"};
       virtual System::ComponentModel::TypeConverter::StandardValuesCollection ^ GetStandardValues(System::ComponentModel::ITypeDescriptorContext ^ context) override
       {
           return gcnew StandardValuesCollection(alignmode);
       }
       virtual bool GetStandardValuesSupported(System::ComponentModel::ITypeDescriptorContext ^ context) override
       {
          return true;
       }
       virtual bool GetStandardValuesExclusive(System::ComponentModel::ITypeDescriptorContext ^ context) override
       {
          return true;
       }
   };

Vulpes · Answer

I've found this MSDN article on the PropertyGrid control and it appears that to convert from a listbox to a combobox style may be as simple as returning 'false' from your override of the GetStandardValuesExclusive method. Search for the second occurrence of the word 'combo': http://msdn.microsoft.com/en-us/library/aa302326.aspx?ppud=4

Vulpes · Answer

He certainly is though Sam is still leading the 'Top Contributors' table :) Also, Javeed has made a promising start and I wouldn't be surprised to see him challenging them for top honors in due course.

Suthish Nair · Answer

We got a VC++ (VulpesC++) guru here. :)

Sam Hobbs · Answer

Thank you, Suthish. I will try to create a thread with a list; I think that would be better than posting here.

Suthish Nair · Answer

Am charging up, hope I get more free time in coming months. Sam, I can give a try for your questions. :)

Sam Hobbs · Answer

I will be very impressed if a member here could answer the questions I have asked here.

Karthik Agarwal · Answer

Looks like Suthish is guru of C#.

Vulpes · Answer

I'm hardly a guru, Suthish, but I can still string a few lines together in C++ despite using C# most of the time nowadays :)

Karthik Agarwal · Answer

Yup even though it's a very small change in the code we learnt very much about the properties i hope. Even i didn't do much on the dynamic property changes. Thanks Vulpes.

Vulpes · Answer

We've both learned something there, though it's been a while since I did anything myself in this area :)

Karthik Agarwal · Answer

Happy to say you that it worked but it just requires changing a single line. As you said i just changed GetStandardValuesExclusive to false rather true then it just turned down into editable dropdown just like combobox. Thanks Vulpes. Please refer the code which i changed into red color in the code which i posted in the one which works just like combobox.

Karthik Agarwal · Answer

Yup i want it to work like combobox where in we can type or even choose from the dropdown. And if it comes to sample code the one which i posted first " DrawColor " is an editable dropdown. i want to resemble the same but with the code which i posted above. [Description ("Foreground color"), Category ("Text Configuration")] property Color DrawColor { Color get() { return draw_color; } void set( Color val ) { draw_color = val; } } For any clarifications please feel free to post back.

Vulpes · Answer

Can you explain what you mean by an 'editable' dropdown? If you mean that the user can type in a selection as well as selecting it from the dropdown (i.e. like a combobox rather than a listbox), then I didn't know that was even possible within a standard PropertyGrid. Do you have some sample code that you're working from to do this?

Karthik Agarwal · Answer

I tried doing it Vulpes but i was able to make it dropdown alone didn;t succeed in making into editable dropdown. Below the code which i wrote, can you help me out on making it editable at the earliest. [Description ("Sample text to be displayed in viewer"), Category ("Text Configuration")] [TypeConverter(SidTextList::typeid)] property String ^ TestString { String ^ get() { return sample_text; } void set( String ^ val ) { array ^ space_delimiter = gcnew array (1); space_delimiter[0] = ' '; array ^ splitted_sid; splitted_sid = val->Split(space_delimiter); String ^ concat_text; int len = splitted_sid->Length; for each(KeyValuePair ^> kvp in SidLanguageData->language_string_table) { if(SidLanguageData->copy_of_clicked_language == "View " + kvp.Key) { concat_text = ""; for(int j = 0;j { if(splitted_sid[j] != "") { for(int x = 0;x language_string_id->Length;x++) { if(splitted_sid[j] == SidLanguageData->language_string_id[x]) { List ^ values = kvp.Value; if(len > 1) { concat_text = concat_text + values[x]->ToString(); sample_text = concat_text; } else { sample_text = values[x]->ToString(); } } } } if(splitted_sid[j]->StartsWith("X") && splitted_sid[j]->EndsWith("X")) { if(len > 1) { concat_text = concat_text + splitted_sid[j]->Replace("X", SidLanguageData->max_dec_string); sample_text = concat_text; } else { sample_text = val->Replace("X", SidLanguageData->max_dec_string); } } else if(splitted_sid[j]->StartsWith("Y") && splitted_sid[j]->EndsWith("Y")) { if(len > 1) { concat_text = concat_text + splitted_sid[j]->Replace("Y", SidLanguageData->max_string); sample_text = concat_text; } else { sample_text = val->Replace("Y", SidLanguageData->max_string); } } else if(splitted_sid[j]->StartsWith("'") && splitted_sid[j]->EndsWith("'")) { if(len > 1) { concat_text = concat_text + splitted_sid[j]->Replace("'", ""); sample_text = concat_text; } else { sample_text = val->Replace("'", ""); } } } } } sample_text = val; } } public ref class SidTextList : System::ComponentModel::StringConverter { public: virtual System::ComponentModel::TypeConverter::StandardValuesCollection ^ GetStandardValues(System::ComponentModel::ITypeDescriptorContext ^ context) override { return gcnew StandardValuesCollection(Globals::sid_text_listbox->Items); } virtual bool GetStandardValuesSupported(System::ComponentModel::ITypeDescriptorContext ^ context) override { return true; } virtual bool GetStandardValuesExclusive(System::ComponentModel::ITypeDescriptorContext ^ context) override { return true; // return false //EDITED it should be false to make it work like combobox } };

Vulpes · Answer

Yes, you should be able to deal with that property in an analogous way. If you can let me have a list of the possible values, I'll see if I can write the code for you when I next get time.

Karthik Agarwal · Answer

Pretty hard to understand but what i need is to have a dropdown which can be edited. so how can i do that for the following property? property String ^ StringSelect { String ^ get() { return sample_string; } void set( String ^ val ) { sample_string = val; } }

Vulpes · Answer

If you've created a custom control and you want to add design type support for it to the Properties Box, then there may be some properties where you'd like to display a dropdown list for the user to choose from. You can do this using a type converter for the property's type. Here you have a reference type called AlignModeList which inherits from StringConverter which itself inherits from the TypeConverter base class. TypeConverter has virtual methods called GetStandardValues, GetStandardValuesSupported and GetStandardValuesExclusive which are being overridden here in the derived class. The AlignModeList class also has a static string array field called alignmode which has 3 elements: "Left", "Centre" and "Right". The GetStandardValues method creates and returns a new StandardValuesCollection object from these three elements. The other two methods return a bool (always true) to indicate that all these values are supported exclusively within the dropdown list The AlignModeList TypeConverter is then applied (using an attribute which identifies it by its typeid property) to a string property called Alignment. This property has a backing field called 'alignment' (not shown in the snippet) to store the current setting: "Left", "Centre" or "Right" which is get or set in the usual fashion. The property also has Description and Category attributes for displaying its description and the category to which it is to be allocated within the Properties Box. DrawColor is another property to be used at design time whose backing field is called draw_color and which has Description and Category attributes. However, this is of the standard Color type and so doesn't need a custom type descriptor to display its possible values - the ColorDialog will be displayed instead.