windows form窗体应用程序，建一个记事本参考代码，重点是打开，保存，另存为

     //当点击打开的时候
        private string files;  //建一个成员变量，用来存储打开的路径
        private void 打开OToolStripMenuItem_Click(object sender, EventArgs e)
        {
            //openFileDialog1.Filter = "文本文件|*txt|视频文件|*avi;*jpg"; //filter建立一个筛选器
            //openFileDialog1.ShowDialog();
            DialogResult isok = openFileDialog1.ShowDialog();
            if (isok == DialogResult.OK) //判断是否点击的打开按钮
            {
                string filename = openFileDialog1.FileName;//获取文件路径,文件路径存在FileName里
                //使用流进行文件读取
                StreamReader sr = new StreamReader(filename); //构建一个streamreader类的对象sr ,文件路径作为参数
                textBox1.Text = sr.ReadToEnd();   //readtoend方法，把文件完全读出
                sr.Close();  //流用完一定关闭
                files = filename;
            }
//当点击另存为按钮的时候
        private void 保存sToolStripMenuItem_Click(object sender, EventArgs e)
        {
            saveFileDialog1.Filter = "文本文件|*.txt";   //要保存的文件格式。Filter文件筛选器
            DialogResult isok = saveFileDialog1.ShowDialog();  //是否点击保存按钮
            if (isok==DialogResult .OK)
            {
                string filename = saveFileDialog1.FileName;
                StreamWriter sw = new StreamWriter(filename);
                sw.Write(textBox1.Text);
                sw.Close(); //流用完一定要关闭
            }
            MessageBox.Show(saveFileDialog1 .FileName );
        }

        //当点击保存按钮的时候
        private void 另存为AToolStripMenuItem_Click(object sender, EventArgs e)
        {
            if (files == null)
            {
                DialogResult baocun = saveFileDialog1.ShowDialog();
                if (baocun == DialogResult.OK)
                {
                    string filename = saveFileDialog1.FileName;
                    StreamWriter sw = new StreamWriter(filename);
                    sw.Write(textBox1.Text);
                    sw.Close();
                }
            }
            else
            {
                StreamWriter sw = new StreamWriter(files);
                sw.Write(textBox1.Text);
                sw.Close();
            }
        }
  //当点击颜色的时候
        private void 颜色ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            //colorDialog1.ShowDialog();//显示颜色对话框，要显示对话框都有showdialog这个共同属性。。 colorDialog1.ShowDialog()会有一个返回值，用dialogresult这个枚举类型来接受
            DialogResult dr = colorDialog1.ShowDialog();
            if (dr==DialogResult .OK)  //判断是否点击的确定按钮
            {
                this.BackColor = colorDialog1.Color;  //如果仅仅写这一句代码，在选完颜色之后点取消，会默认系统里的一个黑色
            }

        }
        //点击文件浏览器获取路径
        private void 文件浏览器ToolStripMenuItem_Click(object sender, EventArgs e)
        {
            DialogResult dr = folderBrowserDialog1.ShowDialog();   //接受打卡文件路径时的返回值
            if (dr==DialogResult .OK)
            {
                MessageBox.Show(folderBrowserDialog1.SelectedPath );  //selectedpath获取路径的属性
            }
        }
  //当点击新建的时候
        private void 新建NToolStripMenuItem_Click(object sender, EventArgs e)
        {
            if (textBox1 .Text .Length>0)
            {
                saveFileDialog1.ShowDialog();
                DialogResult dr = new DialogResult();
                if (dr == DialogResult.OK)
                {
                    string filename = saveFileDialog1.FileName;
                    StreamWriter sw = new StreamWriter(filename);
                    sw.Write(textBox1.Text);
                    sw.Close();
                }
                else
                {
                    textBox1.Text = "";
                }
            }
        }