C# 自定义控件类库（带checkbox的combox控件）

最近喜欢上了自己创建控件，感觉方便使用

其实自定义控件，除了之前说的自己建立个独立的控件库的方法外，另一个办法就是通过继承已有的控件来扩展功能

今天就是用这个办法，在combox的控件中扩展个check功能，这样就可以有选择的选择多条Item了。

其实主要的步骤就是：1.定义属性和各个属性的读写  2.定义方法和各种函数实现功能 3.关联各种方法和事件触发

首先，要确定框架

using System;
using System.Collections;
using System.Collections.Generic;
using System.Data;
using System.Drawing;
using System.Diagnostics;
using System.Windows.Forms;
namespace PowerComboBox //带有复选框的combox
{
    public class xComboBox : ComboBox
    {
        public xComboBox()
        {
        this.DrawMode =System.Windows.Forms.DrawMode.OwnerDrawFixed; //这是关键；没有这一步自定义的控件无法显示出来
        }
    }
}

　　下来我们就要看看需要定义什么样的属性了

     

    private string mDividerFormat = "";
    private Color mGroupColor = System.Drawing.SystemColors.WindowText; //分组的背景颜色
    private System.Windows.Forms.CheckState[] mItemsChecks;//用来记录选中的状态，那些选中，那些没选中。只要读这里就知道。
    private System.Windows.Forms.CheckState[] mItemsChecks_Temp;
    private bool mCheckBoxes; //是否使用复选框
    private System.Windows.Forms.CheckState mChecked = CheckState.Unchecked; //默认的选中状态
    private Color mGridColor = Color.FromArgb(240, 248, 255);//条目的背景颜色

　　各种变量

    private char mItemSeparator1 = ',';//用来分隔多条选中信息的
    private char mItemSeparator2 = '&';//同上
    private Int32 mHoverIndex;
    private double mHoverIndex_Dec;
    private Int32 mLastSelectedIndex = -1;
    private Timer mTimer;//定时器，用来控制在Item选中状态变化过程中，发生的事
    private Int32 mFirerTimer;
    private Int32 mKillEvents1; 
    private Int32 mKillEvents2; 
    private Int32 mKillEvents3; 
    private Int32 mLastMessage;

　　再来看看各个变量的读写设置

  [System.ComponentModel.Description("Use this property to set divider flag.  Recommend you use three hyphens ---."), System.ComponentModel.Category("Power Properties")] //这种写法就是要将属性在属性页中显示的样子（请参照我之前写的Property Grid的内容）
    public string DividerFormat
    {
    get
    {
        return mDividerFormat;
    }
    set
    {
        mDividerFormat = value;
    }
    }
    [System.ComponentModel.Description("Use this property to set the ForeColor of the grouping text."), System.ComponentModel.Category("Power Properties")]
    public Color GroupColor
    {
    get
    {
        return mGroupColor;
    }
    set
    {
        mGroupColor = value;
    }
    }
    [System.ComponentModel.Description("Use this property to set the BackColor of the grid."), System.ComponentModel.Category("Power Properties")]
    public Color GridColor
    {
    get
    {
        return mGridColor;
    }
    set
    {
        mGridColor = value;
    }
    }
//ORIGINAL LINE: Public Property ItemsChecks(ByVal xIndex As Int32) As System.Windows.Forms.CheckState
//INSTANT C# NOTE: C# does not support parameterized properties - the following property has been divided into two methods:
    [System.ComponentModel.Description("Use this property to get/set corresponding checkboc values."), System.ComponentModel.Category("Power Properties")]
    public System.Windows.Forms.CheckState get_ItemsChecks(Int32 xIndex)
    {
        try
        {
        return mItemsChecks[xIndex];
        }
        catch (Exception ex)
        {
        return CheckState.Unchecked;
        }
    }
    public void set_ItemsChecks(Int32 xIndex, System.Windows.Forms.CheckState value) //将条目的序号和选中状态配对mItemsChecks[xIndex] = value
        {

            if (xIndex < 0 | xIndex > this.Items.Count)
            {
                return;
            }

            if (mKillEvents3 != 0)
            {
                mItemsChecks[xIndex] = value;  //mItemsChecks[xIndex] = value;将条目序号和状态对应
            if (ItemChecked != null)
                ItemChecked(SelectedIndex);
            }
            else
            {
                if (this.CheckBoxes)//如果已经选定check功能
                {
                    if (this.DroppedDown)//
                    {
                        if (this.SelectedIndex == xIndex)
                        {
                            this.SelectedIndex = -1;
                        }
                    this.SelectedIndex = xIndex;
                    PrepareTimer();
                    if (ItemChecked != null)
                        ItemChecked(SelectedIndex); //raises event immeadiatly
                    }
                    else
                    {

                        if (mItemsChecks == null)
                        {
                        Array.Resize(ref mItemsChecks_Temp, this.Items.Count);
                        mItemsChecks_Temp[xIndex] = value;
                        CommitCheckList();
                        }
                        else
                        {
                        mItemsChecks[xIndex] = value;
                        }

                    }
                }
            }

        }
    [System.ComponentModel.Description("Use this property to enable checkboxes."), System.ComponentModel.Category("Power Properties")]
    public bool CheckBoxes
    {
        get
        {
        return mCheckBoxes;
        }
        set
        {
        mCheckBoxes = value;
        }
    }
    [System.ComponentModel.Description("Use this property to set CheckBox's default value."), System.ComponentModel.Category("Power Properties")]
    public System.Windows.Forms.CheckState Checked
    {
        get
        {
        return mChecked;
        }
        set
        {
        mChecked = value;
        }
    }
    [System.ComponentModel.Description("Use this property to set item separator1 character."), System.ComponentModel.Category("Power Properties")]
    public char ItemSeparator1
    {
        get
        {
        return mItemSeparator1;
        }
        set
        {
        mItemSeparator1 = value;
        }
    }
    [System.ComponentModel.Description("Use this property to set item separator2 character."), System.ComponentModel.Category("Power Properties")]
    public char ItemSeparator2
    {
        get
        {
        return mItemSeparator2;
        }
        set
        {
        mItemSeparator2 = value;
        }
    }

　　

下来就是事件方法了

其实大体的流程就是在选择了check功能后，下拉菜单在打开时重新绘制个带check的Items。然后在选中某个Item项时，combox的Text中就重新显示说有checked的项目

protected override void OnSelectedIndexChanged(System.EventArgs e)//当选项的check状态被选中时
    {
    Int32 i = 0;
        if (mKillEvents1 != 0 || SelectedIndex == -1)
        {
            return;
        }
            if (this.DividerFormat.Length > 0 && IsItemAGroup(SelectedIndex))
            {
                if (! this.CheckBoxes)
                {
                this.SelectedIndex = mLastSelectedIndex;
                return;
                }
                else
                {
                mKillEvents3 += 1;
                i = SelectedIndex;
                    do
                    {
                    i += 1;
                        if (i > (this.Items.Count - 1))
                        {
                            break;
                        }
                        if (IsItemAGroup(i))
                        {
                            break;
                        }
                    this.SelectedIndex = i;
                    } while (true);
                mKillEvents3 -= 1;
                base.OnSelectedIndexChanged(e);
                return;
                }
            }
        //2 - standard event stuff
        mLastSelectedIndex = this.SelectedIndex;
        base.OnSelectedIndexChanged(e);
            //3 - toggle checkbox/force redraw
            if (this.CheckBoxes && SelectedIndex > -1)
            {
            mKillEvents3 += 1;
                if (this.get_ItemsChecks(this.SelectedIndex) == CheckState.Checked)
                {
                this.set_ItemsChecks(this.SelectedIndex, CheckState.Unchecked);
                }
                else
                {
                this.set_ItemsChecks(this.SelectedIndex, CheckState.Checked);
                }
            mKillEvents3 -= 1;
            PrepareTimer();
            }
    }
    protected override void OnDrawItem(DrawItemEventArgs e)//重新绘制Item，根据用户是否选择了check定义item项的样子
    {
    Int32 zX1 = 0;
    Pen zPen = null;
    float zWidth = 0F;
    string zText = null;
    Font zFont = null;
    Color zFore = new Color();
    System.Windows.Forms.VisualStyles.CheckBoxState zState = 0;
            //1 - Exit
            if (e.Index < 0)
            {
            base.OnDrawItem(e);
            return;
            }
            //2 - Grouping
            if (this.Items[e.Index].ToString().Contains(this.mDividerFormat) & mDividerFormat.Length > 0)
            {
            e.DrawBackground();
                if (DataSource == null) //TN Engineers
                {
                zText = this.Items[e.Index].ToString();
                }
                else
                {
                zText = ((DataRowView)(this.Items[e.Index]))[this.DisplayMember].ToString();
                }
            zText = this.Items[e.Index].ToString();
            zText = " " + zText.Replace(this.mDividerFormat, "") + " ";
            zFont = new Font(Font, FontStyle.Bold);
                if (e.BackColor == System.Drawing.SystemColors.Highlight)
                {
                zFore = Color.Gainsboro;
                }
                else
                {
                zFore = this.GroupColor;
                }
            zPen = new Pen(zFore);
            zWidth = e.Graphics.MeasureString(zText, zFont).Width;
            zX1 = Convert.ToInt32(e.Bounds.Width - zWidth) / 2;
            e.Graphics.DrawRectangle(zPen, new Rectangle(e.Bounds.X, e.Bounds.Y + e.Bounds.Height / 2, zX1, 1));
            e.Graphics.DrawRectangle(zPen, new Rectangle(e.Bounds.Width - zX1, e.Bounds.Y + e.Bounds.Height / 2, e.Bounds.Width, 1));
            e.Graphics.DrawString(zText, zFont, new SolidBrush(zFore), zX1, e.Bounds.Top);
            }
            else
            {
          
                if (mKillEvents2 == 0)
                {

                    if (true == System.Convert.ToBoolean(e.State & DrawItemState.Selected))
                    {
                    e.DrawBackground();
                    }
                    else if (true == (e.Index % 2 == 0))
                    {
                    e.Graphics.FillRectangle(new SolidBrush(Color.White), e.Bounds);
                    }

                    else
                    {
                    e.Graphics.FillRectangle(new SolidBrush(mGridColor), e.Bounds);
                    }
                }
               
                if (this.DataSource == null) 
                {
                e.Graphics.DrawString(this.Items[e.Index].ToString(), Font, new SolidBrush(e.ForeColor), e.Bounds.Left, e.Bounds.Top);
                }
                else
                {
                e.Graphics.DrawString(((DataRowView)(this.Items[e.Index]))[this.DisplayMember].ToString(), Font, new SolidBrush(e.ForeColor), e.Bounds.Left, e.Bounds.Top);
                }
                //5 - CheckBox
                if (mCheckBoxes)
                {
                        if (System.Convert.ToBoolean(e.State & DrawItemState.Selected))
                        {
                            if (this.get_ItemsChecks(e.Index) == CheckState.Checked)
                            {
                            zState = System.Windows.Forms.VisualStyles.CheckBoxState.CheckedHot;
                            }
                            else
                            {
                            zState = System.Windows.Forms.VisualStyles.CheckBoxState.UncheckedHot;
                            }
                        }
                        else
                        {
                            if (this.get_ItemsChecks(e.Index) == CheckState.Checked)
                            {
                            zState = System.Windows.Forms.VisualStyles.CheckBoxState.CheckedNormal;
                            }
                            else
                            {
                            zState = System.Windows.Forms.VisualStyles.CheckBoxState.UncheckedNormal;
                            }
                        }
                zX1 = this.FontHeight;
                zPen = new Pen(Color.Black, 1F);
                zPen.DashStyle = System.Drawing.Drawing2D.DashStyle.Dot;
                System.Windows.Forms.CheckBoxRenderer.DrawCheckBox(e.Graphics, new System.Drawing.Point(e.Bounds.X + e.Bounds.Width - 15, e.Bounds.Y + 1 + ((e.Bounds.Height - 13) / 2)), e.Bounds, "", this.Font, false, zState);
                }
            }
        //6 - Base event
        base.OnDrawItem(e);
    }
    protected override void WndProc(ref System.Windows.Forms.Message m)//消息处理
    {
    const Int32 WM_SETCURSOR = 32;
    const Int32 WM_COMMAND = 273;
    const int WM_CTLCOLORLISTBOX = 308;
    const Int32 CB_ADDSTRING = 323;
    const Int32 CB_GETCURSEL = 327;
    const Int32 WM_LBUTTONUP = 514;
    const Int32 OCM_COMMAND = 8465;
            if (true == (m.Msg == WM_CTLCOLORLISTBOX || m.Msg == WM_SETCURSOR))
            {
            GetHoverIndexFromCursor();
                if (mHoverIndex_Dec >= 0)
                {
                    if (mHoverIndex > -1 & mHoverIndex < this.Items.Count & this.DroppedDown)
                    {
                    if (ItemHover != null)
                        ItemHover(mHoverIndex);
                    }
                }
            }

            else if (true == (m.Msg == CB_ADDSTRING))
            {
            base.WndProc(ref m);
            StretchCheckList();
            return;
            }
            else if (true == (m.Msg == WM_COMMAND && m.WParam == new System.IntPtr(66536)))
            {
                if (mLastMessage == 8235) //FIX for ignoring SIC event on keyboard controlling i.e. F4 + down arrow
                {
                mHoverIndex = this.SelectedIndex;
                if (ItemHover != null)
                    ItemHover(mHoverIndex);
                mLastMessage = m.Msg;
                return;
                }
                //1 - normal behaviour when no checkboxes
                if (! this.mCheckBoxes)
                {
                base.WndProc(ref m);
                return;
                }
                if (! this.DroppedDown)
                {
                return;
                }
            SendMessage(this.Handle, OCM_COMMAND, 591814, new IntPtr(1705748)); //1
            SendMessage(this.Handle, OCM_COMMAND, 67526, new IntPtr(1705748)); //2
            SendMessage(this.Handle, CB_GETCURSEL, 0, new IntPtr(0)); //3
            SendMessage(this.Handle, WM_LBUTTONUP, 0, new IntPtr(721012)); //4
            return;
            }

        mLastMessage = m.Msg;
        base.WndProc(ref m);

    }
    protected override void OnKeyDown(System.Windows.Forms.KeyEventArgs e) //键盘事件
    {

            if (this.DroppedDown && e.KeyCode == Keys.Space)
            {
            mKillEvents3 += 1;
            e.SuppressKeyPress = true;
                if (this.CheckBoxes)
                {
                    if (this.get_ItemsChecks(this.SelectedIndex) == CheckState.Checked) //如果选择的条目是被选中的状态
                    {
                    this.set_ItemsChecks(this.SelectedIndex, CheckState.Unchecked);//则是变反
                    }
                    else
                    {
                    this.set_ItemsChecks(this.SelectedIndex, CheckState.Checked);
                    }
                mKillEvents3 -= 1;
                }
                else //如果没有选用check的形式条目，那么就不用处理
                {
                this.DroppedDown = false;
                }
            PrepareTimer(); //时间空间处理刷新text
            }

        base.OnKeyDown(e);

    }

　　下面是方法中用到的各个处理方法

private void PrepareTimer() //通过时间控件来刷新combox的text显示的内容
    {
        mTimer = null;
        mTimer = new Timer();
        mTimer.Interval = 64;
        mTimer.Enabled = true;
        mTimer.Tick += mTimer_Tick;
        mFirerTimer = 1;
    }
    private void mTimer_Tick(object sender, System.EventArgs e)
    {
        if (mFirerTimer > 0)
        {
        mTimer.Enabled = false;
        mTimer.Dispose();
        ForceRedraw(); 
        this.Text = FormatCheckString(); //将选中的显示出来
        mFirerTimer = 0;//判断是否启动timer控件的
        }
    }
    public void StretchCheckList()
    {
    Int32 i = 0;
        Array.Resize(ref mItemsChecks, this.Items.Count);
            //1. suck in temp
            if (mItemsChecks_Temp != null)
            {
            mItemsChecks = mItemsChecks_Temp;
            mItemsChecks_Temp = null;
            //2. formats list with pre-defined format
            }
            else
            {
                if (mChecked != CheckState.Checked)
                {
                    return;
                }
                for (i = 0; i <= mItemsChecks.GetUpperBound(0); i++)
                {
                    if (! (IsItemAGroup(i)))
                    {
                        mItemsChecks[i] = CheckState.Checked;
                    }
                }
            }
        this.Text = FormatCheckString();
    }
    public void CommitCheckList()
    {
        mItemsChecks = mItemsChecks_Temp;
        this.Text = FormatCheckString();
    }
//private
    private void GetHoverIndexFromCursor()
    {
    Int32 yPos = 0;
        yPos = this.PointToClient(System.Windows.Forms.Cursor.Position).Y;
            if (this.DropDownStyle == ComboBoxStyle.Simple)
            {
            yPos -= (this.ItemHeight + 10);
            }
            else
            {
            yPos -= (this.Size.Height + 1);
            }
        mHoverIndex_Dec = yPos / (double)this.ItemHeight;
        mHoverIndex = System.Convert.ToInt32(Math.Floor(mHoverIndex_Dec));
    }
    private void ForceRedraw()
    {
            if (this.Items.Count > 0)
            {
            mKillEvents1 += 1;
            mKillEvents2 += 1;
            this.SelectedIndex -= 1;
            mKillEvents2 -= 1;
            this.SelectedIndex += 1;
            mKillEvents1 -= 1;
            }
    }
    private string FormatCheckString() //形成text
    {
//NOTE returns "a,b & c" for internal use
    Int32 i = 0;
    System.Text.StringBuilder sb = new System.Text.StringBuilder("");
    string s = null;
    string zFirst = null;
    string zLast = null;
    Int32 zLastComa = 0;
    string zSpace = " ";
            if (! this.CheckBoxes) //首先要确定是check的item
            {
                return this.Text;
            }
            for (i = 0; i < this.Items.Count; i++)
            {
                if (IsItemAGroup(i)) //什么意思啊
                {
                    continue;
                }
                if (this.get_ItemsChecks(i) == CheckState.Checked)//确定选项是被选中的
                {
                    if (DataSource == null) //TN Engineers
                    {
                    sb.Append(this.Items[i].ToString());
                    }
                    else
                    {
                    sb.Append(((DataRowView)(this.Items[i]))[this.DisplayMember].ToString());
                    }
                sb.Append(mItemSeparator1); //没加一项就加一个分隔符&
                }
            }
        s = sb.ToString();
            if (s.Length == 0)
            {
                return "";
            }
        s = s.Substring(0, s.Length - 1);
        zLastComa = s.LastIndexOf(mItemSeparator1);
            if (zLastComa != -1)
            {
            zLast = s.Substring(zLastComa);
            zFirst = s.Substring(0, zLastComa);
            s = zFirst + zSpace + zLast.Replace(Convert.ToString(mItemSeparator1), Convert.ToString(mItemSeparator2) + zSpace);
            return s;
            }
            else
            {
            return s + " ";
            }
    }
    private bool IsItemAGroup(Int32 xIndex)
    {
            if (this.mDividerFormat.Length > 0 && this.Items[xIndex].ToString().Contains(this.mDividerFormat))
            {
                return true;
            }
//INSTANT C# NOTE: Inserted the following 'return' since all code paths must return a value in C#:
            return false;
    }
//public
    public string CHECKED2CSV()
    {
//NOTE returns "a,b,c" for external user
    Int32 i = 0;
    System.Text.StringBuilder sb = new System.Text.StringBuilder("");
    string s = null;
            for (i = 0; i < this.Items.Count; i++)
            {
                if (IsItemAGroup(i))
                {
                    continue;
                }
                if (this.get_ItemsChecks(i) == CheckState.Checked)
                {
                    if (DataSource == null) //TN Engineers
                    {
                    sb.Append(this.Items[i].ToString() + ",");
                    }
                    else
                    {
                    sb.Append(((DataRowView)(this.Items[i]))[this.ValueMember].ToString() + ",");
                    }
                }
            }
        s = sb.ToString();
            if (s.Length > 0)
            {
                s = s.Substring(0, s.Length - 1);
            }
        return s;
    }

    public string CHECKED2IDCSV()
    {
        return CHECKED2IDCSV(true);
    }

//INSTANT C# NOTE: Overloaded method(s) are created above to convert the following method having optional parameters:
//ORIGINAL LINE: Public Function CHECKED2IDCSV(Optional ByVal xZeroBound As Boolean = true) As String
    public string CHECKED2IDCSV(bool xZeroBound)
    {
    Int32 i = 0;
    Int32 c = 0;
    Int32 a = 0;
    System.Text.StringBuilder sb = new System.Text.StringBuilder("");
    string s = null;
            if (xZeroBound)
            {
                a = 0;
            }
            else
            {
                a = 1;
            }
            for (i = 0; i < this.Items.Count; i++)
            {
                if (IsItemAGroup(i))
                {
                    continue;
                }
                if (this.get_ItemsChecks(i) == CheckState.Checked)
                {
                    if (this.mDividerFormat.Length > 0)
                    {
                    sb.Append((c + a).ToString() + ",");
                    }
                    else
                    {
                    sb.Append((i + a).ToString() + ",");
                    }
                }

            c += 1;
            }
        s = sb.ToString();
            if (s.Length > 0)
            {
                s = s.Substring(0, s.Length - 1);
            }
        return s;
    }
    public string CHECKED2BITSHIFT()
    {
    Int32 i = 0;
    Int32 c = 1;
    Int32 a = 0;
            for (i = 0; i < this.Items.Count; i++)
            {
                if (IsItemAGroup(i))
                {
                    continue;
                }
                if (this.get_ItemsChecks(i) != CheckState.Checked)
                {
                a += c;
                }
            c = (c * 2);
            }
        return a.ToString();
    }
    public void CheckAll(CheckState xChecked)
    {
    Int32 i = 0;
            for (i = 0; i < this.Items.Count; i++)
            {
            this.set_ItemsChecks(i, xChecked);
            }
        this.Text = FormatCheckString();
    }

　　其实知道了流程，完全就可以自定义控件来使用。方便好用