UITypeEditor for System.Type

Question

I have a property DataType which contains a value of System.Type.  I want to have a UITypeEditor that brings up a dropdown of all the System.Types.  I've got as far as creating a "DataTypeEditor" which inherits from UITypeEditor and GetEditStyle returns UiEditorEditStyle.DropDown.  I know I need to override EditValue, but I am not sure how to create an editor control ot display all the System.Type values.  Can anyone point me in a direction?  Thanks.

Answer 1

 

Hi LiteWait,

We can get all types of current project with reflection. Try the following code:

Code Snippet

using System.Reflection;

namespace FormP

{

    public partial class Form10 : Form

    {

        public Form10()

        {

            InitializeComponent();

        }

 

        private void button1_Click(object sender, EventArgs e)

        {

            Assembly[] array = AppDomain.CurrentDomain.GetAssemblies();

            foreach (Assembly a in array)

            {

                this.treeView1.Nodes.Add(a.GetName().Name,a.GetName().Name);

                Type[] types = a.GetTypes();

                foreach (Type t in types)

                {

                    if (t.IsPublic)

                        this.treeView1.Nodes[a.GetName().Name].Nodes.Add(t.FullName);

                }

            }

            treeView1.ExpandAll();

        }

    }

}

 

You can create a UserControl with a TteeView in it. The TreeView is used to show all valid types. And then make the UserControl as the editor control of your ‘DataTypeEditor’.

Best regards.
Rong-Chun Zhang

Answer 2

There is no need to use a type editor as a type converter will suffice:

 

using System;

using System.Reflection;

using System.Globalization;

using System.ComponentModel;

using System.Collections.Generic;

 

public class DataTypeConverter : TypeConverter

{

   public override bool CanConvertTo (ITypeDescriptorContext context, Type destinationType)

   {

      bool canConvertTo = false;

 

      if (destinationType == typeof(string))

      {

         canConvertTo = true;

      }

      else

      {

         canConvertTo = base.CanConvertTo(context, destinationType);

      }

 

      return canConvertTo;

   }

 

   public override object ConvertTo (ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)

   {

      object convertedValue = null;

      Type instance = null;

 

      if (value is Type)

      {

         instance = (Type)value;

      }

 

      if (destinationType == typeof(string))

      {

         if (value is string)

         {

            convertedValue = value;

         }

         else if (instance != null)

         {

            convertedValue = instance.Name;

         }

      }

      else

      {

         convertedValue = base.ConvertTo(context, culture, value, destinationType);

      }

 

      return convertedValue;

   }

 

   public override bool CanConvertFrom (ITypeDescriptorContext context, Type sourceType)

   {

      bool canConvertFrom = false;

 

      if (sourceType == typeof(string))

      {

         canConvertFrom = true;

      }

      else

      {

         canConvertFrom = base.CanConvertFrom(context, sourceType);

      }

 

      return canConvertFrom;

   }

 

   public override object ConvertFrom (ITypeDescriptorContext context, CultureInfo culture, object value)

   {

      object convertedValue = null;

 

      if (value is string)

      {

         // all types represented by TypeCode are in the System namespace.

         convertedValue = Type.GetType("System." + value);

      }

      else

      {

         convertedValue = base.ConvertFrom(context, culture, value);

      }

 

      return convertedValue;

   }

 

   public override bool GetStandardValuesSupported (ITypeDescriptorContext context)

   {

      return true;

   }

 

   public override TypeConverter.StandardValuesCollection GetStandardValues (ITypeDescriptorContext context)

   {

      List<string> typeList = new List<string>(Enum.GetNames(typeof(TypeCode)));

 

      // remove the two "non-standard" types.

      typeList.Remove("DBNull");

      typeList.Remove("Empty");

      string[] typeArray = typeList.ToArray();

      Array.Sort(typeArray);

      return new TypeConverter.StandardValuesCollection(typeArray);

   }

 

   public override bool GetStandardValuesExclusive (ITypeDescriptorContext context)

   {

      // return true here if you want to not allow the

      // user to enter a value that is not in the list.

      return false;

   }

}