1，我遇到的问题是再写控件库的扩展类时，没有加public关键字，如

 public class MyListView: System.Windows.Forms.ListView

 {

。。。。

}

如果去掉 public 也可以生成DLL，但当你把它添加到用户控件时就会提示：在e:/mylistview/bin/myListView.dll中没有可放置在工具箱上的组件

 

2，控件需要有自己的空的构造函数，即使如果存在带参数的构造函数也应存在空的构造函数

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.ComponentModel;using System.Windows.Forms;using System.Drawing;namespace CustomControlSample{    public class FirstControl : Control    {        public FirstControl()        {        }        private ContentAlignment alignmentValue = ContentAlignment.MiddleLeft;        [        Category("Alignment"),        Description("Specifies the alignment of text.")        ]        public ContentAlignment TextAlignment        {            get { return alignmentValue; }            set             {                alignmentValue = value;                Invalidate();            }        }        protected override void OnPaint(PaintEventArgs e)        {            base.OnPaint(e);            StringFormat style = new StringFormat();            style.Alignment = StringAlignment.Near;            switch (alignmentValue)            {                case ContentAlignment.MiddleLeft:                    style.Alignment = StringAlignment.Near;                    break;                case ContentAlignment.MiddleRight:                    style.Alignment = StringAlignment.Far;                    break;                case ContentAlignment.MiddleCenter:                    style.Alignment = StringAlignment.Center;                    break;            }            e.Graphics.DrawString(                Text,                Font,                new SolidBrush(ForeColor),                ClientRectangle, style);        }    }}