实现RadioButtonList自定义WinForm控件

目的:项目有需要，创建一个支持数据绑定的单选按钮列表。
设想：动态识别多种数据源， 动态生成一定数量的按钮。
准备：创建一个自定义控件，添加一个Panel对象。
优点: 支持多种数据源做绑定，并可以自己添加自定义数据源。
缺点：错误的抛出没有做到位，没有完全做到设计时定义所有数据。原因：懒。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Text;
using System.Windows.Forms;
using System.Collections;

namespace RVProject
{
    public partial class RadioButtonList : UserControl
    {
        Variable#region Variable
        private Object _dataSource;
        private ButtonValueMapping[] _mappings;
        private Object _internalDataSource;
        private string _displayMember;
        private string _valueMember;
        private string _value;
        #endregion
        
        ctor.#region ctor.
        public RadioButtonList()
        {
            InitializeComponent();
        }
        #endregion
        
        prop#region prop
        public System.Object DataSource
        {
            get
            {
                return _dataSource;
            }
            set
            {
                _dataSource = value;
            }
        }
        public string DisplayMember
        {
            get
            {
                return _displayMember;
            }
            set
            {
                _displayMember = value;
            }
        }
        public string ValueMember
        {
            get
            {
                return _valueMember;
            }
            set 
            {
                _valueMember = value;
            }
        }
        public string Value
        {
            get
            {
                return _value;
            }
            set
            {
                if (Value != null)
                {
                    _value = value;
                    SetValue(value);
                }
            }

        }
        #endregion

        event#region event
        public delegate void RadioSelectedHandler(object sender, SelectedEventArgs e);
        public event RadioSelectedHandler RadioItemSeleted;
        #endregion

        public method#region public method
        public void DataBind()
        {
            if (_dataSource == null)
                throw new NullReferenceException("Null reference in Property: DataSource ");
            PrepareData();
            DrawControl();
        }
        #endregion

        //Internal Function
        internal function#region internal function
        void DrawControl()
        {
            panel.Controls.Clear();

            int count = _mappings.Length;
            //Draw and set control
            int height = 0;
            int x_aris = 10;
            int y_aris = 10;
            for (int i = 0; i < count; i++)
            {
                //create the radio button
                RadioButton radio = new RadioButton();
                radio.Name = i.ToString();
                radio.Text = _mappings[i].Text;
                radio.AutoSize = true;
                
                //put radio button into the panel
                panel.Controls.Add(radio);
                radio.Location = new Point(x_aris, y_aris + height);
                height += radio.Height;
                
                //Add click event to radio button
                radio.Click += new EventHandler(radio_Click);
            }


        }
        //Deal with the data source. Add additional code here if you want some new type of objet to be the datasource.
        void PrepareData()
        {
            //deal with the datasouce
            
            if (_dataSource is DataTable)
                _internalDataSource = ((DataTable)_dataSource).DefaultView;
            if (_dataSource is DataView)
                _internalDataSource = _dataSource;
            //Exception
            if (_internalDataSource == null) throw new InvalidCastException("The data source is not a desinged type.");

            //prepare the _radiobutton & _mappings to creat the radio listre
            DataView & DataTable as data source#region DataView & DataTable as data source
            if (_internalDataSource is DataView)
            {
                int radioCount = ((DataView)_internalDataSource).Count;
                _mappings = new ButtonValueMapping[radioCount];
                try
                {
                    for (int i = 0; i < radioCount; i++)
                    {
                        //Set index
                        _mappings[i].Index = i;
                        //Set display text
                        _mappings[i].Text = ((DataView)_internalDataSource)[i][_displayMember].ToString();
                        //Set value
                        if (_valueMember == null || _valueMember == string.Empty)
                        {
                            _mappings[i].Value = i.ToString();
                        }
                        else
                        {
                            _mappings[i].Value = ((DataView)_internalDataSource)[i][_valueMember].ToString();
                        }
                    }
                }
                catch (Exception e)
                {
                    throw e;
                }
            }
            #endregion
        }
        //internal event when a radio button is clicked. this fuction will call a public event.
        void radio_Click(object sender, EventArgs e)
        {
            _value = _mappings[int.Parse(((RadioButton)sender).Name)].Value;
            SelectedEventArgs se = new SelectedEventArgs();
            se.Value = _mappings[int.Parse(((RadioButton)sender).Name)].Value;
            RadioItemSeleted(this, se);
        }
        //When Value changes , the relative radio button is selected.
        void SetValue(string value)
        {
            if (_mappings == null)
                throw new NullReferenceException("Data has not bound to the control");
            foreach(ButtonValueMapping map in _mappings)
            {
                if (map.Value == value)
                {
                    ((RadioButton)panel.Controls[map.Index.ToString()]).Checked = true;
                }
            }
        }
        #endregion

        internal struct ButtonValueMapping
        {
            public int Index;
            public string Value;
            public string Text;
        }

        public class SelectedEventArgs : EventArgs
        {
            public string Value;
        }
    }
}