准备工作

这个窗体继承子基类窗体FrmBase，如果你对FrmBase还不了解，请移步 （十七）c#Winform自定义控件-基类窗体 查看

开始

添加一个Form，命名FrmTransparent，继承自FrmBase

代码不多，直接上完整代码了

// 版权所有  黄正辉  交流群：568015492   QQ：623128629
// 文件名称：FrmTransparent.cs
// 创建日期：2019-08-15 16:05:00
// 功能描述：FrmTransparent
// 项目地址：https://gitee.com/kwwwvagaa/net_winform_custom_control
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Text;
using System.Windows.Forms;

namespace HZH_Controls.Forms
{
    public partial class FrmTransparent : FrmBase
    {
        private const int WM_ACTIVATE = 6;

        private const int WM_ACTIVATEAPP = 28;

        private const int WM_NCACTIVATE = 134;

        private const int WA_INACTIVE = 0;

        private const int WM_MOUSEACTIVATE = 33;

        private const int MA_NOACTIVATE = 3;

        public FrmBase frmchild
        {
            get;
            set;
        }
        public FrmTransparent()
        {
            InitializeComponent();

            base.SetStyle(ControlStyles.UserPaint, true);
            base.SetStyle(ControlStyles.AllPaintingInWmPaint, true);
            base.SetStyle(ControlStyles.DoubleBuffer, true);

            MethodInfo method = base.GetType().GetMethod("SetStyle", BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.InvokeMethod);
            method.Invoke(this, BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.InvokeMethod, null, new object[]
            {
                ControlStyles.Selectable,
                false
            }, Application.CurrentCulture);
        }

        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);
            base.ShowInTaskbar = false;
            base.ShowIcon = true;
        }
        [DllImport("user32.dll")]
        private static extern IntPtr SetActiveWindow(IntPtr handle);

        protected override void WndProc(ref Message m)
        {
            if (m.Msg == 33)
            {
                m.Result = new IntPtr(3);
            }
            else
            {
                if (m.Msg == 134)
                {
                    if (((int)m.WParam & 65535) != 0)
                    {
                        if (m.LParam != IntPtr.Zero)
                        {
                            FrmTransparent.SetActiveWindow(m.LParam);
                        }
                        else
                        {
                            FrmTransparent.SetActiveWindow(IntPtr.Zero);
                        }
                    }
                }
                else if (m.Msg == 2000)
                {
                }
                base.WndProc(ref m);
            }
        }

        private void FrmTransparent_Load(object sender, EventArgs e)
        {
            if (frmchild != null)
            {
                frmchild.IsShowMaskDialog = false;
                var dia = frmchild.ShowDialog(this);
                this.DialogResult = dia;
            }
        }
    }
}

namespace HZH_Controls.Forms
{
    partial class FrmTransparent
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            System.ComponentModel.ComponentResourceManager resources = new System.ComponentModel.ComponentResourceManager(typeof(FrmTransparent));
            this.SuspendLayout();
            // 
            // FrmTransparent
            // 
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.None;
            this.BackColor = System.Drawing.Color.Black;
            this.ClientSize = new System.Drawing.Size(284, 262);
            this.Icon = ((System.Drawing.Icon)(resources.GetObject("$this.Icon")));
            this.Name = "FrmTransparent";
            this.Opacity = 0.5D;
            this.ShowIcon = false;
            this.ShowInTaskbar = false;
            this.StartPosition = System.Windows.Forms.FormStartPosition.CenterParent;
            this.Text = "FrmTransparent";
            this.Load += new System.EventHandler(this.FrmTransparent_Load);
            this.ResumeLayout(false);

        }

        #endregion
    }
}

主要就是构造函数和load事件里面的那几句话

用处及效果

用途：一般用在蒙版，比如弹出窗口的时候，显示一个半透明蒙版

最后的话

如果你喜欢的话，请到 https://gitee.com/kwwwvagaa/net_winform_custom_control 点个星 星吧

作者：冰封一夏
出处： http://www.hzhcontrols.com/doc.html
本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，
且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。
GitHub：https://github.com/kwwwvagaa/NetWinformControl
码云：https://gitee.com/kwwwvagaa/net_winform_custom_control.git