使用Visual Studio写一个简单的Windows窗体应用登录界面

需要的知识：C#的基本语法，以及Visual Studio的基本操作方法

编辑软件：Sql Server 2017，Visual Studio 2017

前提：Sql Server 中有一个名为"MY-LAPTOP"的服务器，一个名为"Test"的数据库，库下有一个名为"Login_Table"的表

一、编写Form1，登录主界面

首先编写Form1.Designer.cs

namespace WindowsFormsApp3
{
    partial class Form1
    {
        /// 

        /// 必需的设计器变量。
        /// 
        private System.ComponentModel.IContainer components = null;

        /// 

        /// 清理所有正在使用的资源。
        /// 
        /// 如果应释放托管资源，为 true；否则为 false。
        protected override void Dispose(bool disposing)
        {
            if (disposing && (components != null))
            {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows 窗体设计器生成的代码

        /// 

        /// 设计器支持所需的方法 - 不要修改
        /// 使用代码编辑器修改此方法的内容。
        /// 
        private void InitializeComponent()
        {
            this.label1 = new System.Windows.Forms.Label();
            this.label2 = new System.Windows.Forms.Label();
            this.button1 = new System.Windows.Forms.Button();
            this.button2 = new System.Windows.Forms.Button();
            this.button3 = new System.Windows.Forms.Button();
            this.textBox1 = new System.Windows.Forms.TextBox();
            this.textBox2 = new System.Windows.Forms.TextBox();
            this.label3 = new System.Windows.Forms.Label();
            this.linkLabel1 = new System.Windows.Forms.LinkLabel();
            this.checkBox1 = new System.Windows.Forms.CheckBox();
            this.SuspendLayout();
            // 
            // label1
            // 
            this.label1.AutoSize = true;
            this.label1.Enabled = false;
            this.label1.Font = new System.Drawing.Font("宋体", 15F);
            this.label1.ForeColor = System.Drawing.SystemColors.ControlText;
            this.label1.Location = new System.Drawing.Point(49, 41);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(87, 25);
            this.label1.TabIndex = 0;
            this.label1.Text = "账号：";
            this.label1.Click += new System.EventHandler(this.label1_Click);
            // 
            // label2
            // 
            this.label2.AutoSize = true;
            this.label2.Enabled = false;
            this.label2.Font = new System.Drawing.Font("宋体", 15F);
            this.label2.ForeColor = System.Drawing.SystemColors.ControlText;
            this.label2.Location = new System.Drawing.Point(49, 98);
            this.label2.Name = "label2";
            this.label2.Size = new System.Drawing.Size(87, 25);
            this.label2.TabIndex = 1;
            this.label2.Text = "密码：";
            this.label2.Click += new System.EventHandler(this.label2_Click);
            // 
            // button1
            // 
            this.button1.Font = new System.Drawing.Font("宋体", 13F);
            this.button1.Location = new System.Drawing.Point(54, 168);
            this.button1.Name = "button1";
            this.button1.Size = new System.Drawing.Size(82, 33);
            this.button1.TabIndex = 2;
            this.button1.Text = "登录";
            this.button1.UseVisualStyleBackColor = true;
            this.button1.Click += new System.EventHandler(this.button1_Click);
            // 
            // button2
            // 
            this.button2.Font = new System.Drawing.Font("宋体", 13F);
            this.button2.Location = new System.Drawing.Point(190, 168);
            this.button2.Name = "button2";
            this.button2.Size = new System.Drawing.Size(90, 33);
            this.button2.TabIndex = 3;
            this.button2.Text = "注册";
            this.button2.UseVisualStyleBackColor = true;
            this.button2.Click += new System.EventHandler(this.button2_Click);
            // 
            // button3
            // 
            this.button3.Font = new System.Drawing.Font("宋体", 13F);
            this.button3.Location = new System.Drawing.Point(329, 168);
            this.button3.Name = "button3";
            this.button3.Size = new System.Drawing.Size(79, 33);
            this.button3.TabIndex = 4;
            this.button3.Text = "取消";
            this.button3.UseVisualStyleBackColor = true;
            this.button3.Click += new System.EventHandler(this.button3_Click);
            // 
            // textBox1
            // 
            this.textBox1.Font = new System.Drawing.Font("宋体", 14F);
            this.textBox1.Location = new System.Drawing.Point(134, 38);
            this.textBox1.Name = "textBox1";
            this.textBox1.Size = new System.Drawing.Size(274, 34);
            this.textBox1.TabIndex = 5;
            // 
            // textBox2
            // 
            this.textBox2.Font = new System.Drawing.Font("宋体", 14F);
            this.textBox2.Location = new System.Drawing.Point(134, 96);
            this.textBox2.Name = "textBox2";
            this.textBox2.PasswordChar = '*';
            this.textBox2.Size = new System.Drawing.Size(274, 34);
            this.textBox2.TabIndex = 6;
            // 
            // label3
            // 
            this.label3.AutoSize = true;
            this.label3.Location = new System.Drawing.Point(54, 217);
            this.label3.Name = "label3";
            this.label3.Size = new System.Drawing.Size(0, 15);
            this.label3.TabIndex = 7;
            // 
            // linkLabel1
            // 
            this.linkLabel1.AutoSize = true;
            this.linkLabel1.Location = new System.Drawing.Point(321, 134);
            this.linkLabel1.Name = "linkLabel1";
            this.linkLabel1.Size = new System.Drawing.Size(83, 15);
            this.linkLabel1.TabIndex = 8;
            this.linkLabel1.TabStop = true;
            this.linkLabel1.Text = "忘记密码>>";
            // 
            // checkBox1
            // 
            this.checkBox1.AutoSize = true;
            this.checkBox1.Location = new System.Drawing.Point(415, 110);
            this.checkBox1.Name = "checkBox1";
            this.checkBox1.Size = new System.Drawing.Size(89, 19);
            this.checkBox1.TabIndex = 9;
            this.checkBox1.Text = "显示密码";
            this.checkBox1.UseVisualStyleBackColor = true;
            this.checkBox1.CheckedChanged += new System.EventHandler(this.checkBox1_CheckedChanged);
            // 
            // Form1
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(8F, 15F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(508, 244);
            this.Controls.Add(this.checkBox1);
            this.Controls.Add(this.linkLabel1);
            this.Controls.Add(this.label3);
            this.Controls.Add(this.textBox2);
            this.Controls.Add(this.textBox1);
            this.Controls.Add(this.button3);
            this.Controls.Add(this.button2);
            this.Controls.Add(this.button1);
            this.Controls.Add(this.label2);
            this.Controls.Add(this.label1);
            this.Name = "Form1";
            this.Text = "Form1";
            this.Load += new System.EventHandler(this.Form1_Load);
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.Label label1;
        private System.Windows.Forms.Label label2;
        private System.Windows.Forms.Button button1;
        private System.Windows.Forms.Button button2;
        private System.Windows.Forms.Button button3;
        private System.Windows.Forms.TextBox textBox1;
        private System.Windows.Forms.TextBox textBox2;
        private System.Windows.Forms.Label label3;
        private System.Windows.Forms.LinkLabel linkLabel1;
        private System.Windows.Forms.CheckBox checkBox1;
    }
}

以下代码中编写了SqlHelp类，其作用是封装连接数据库语句，这样就可以不用每次都编写连接数据库语句，如此便可快速完成编写

如果对SqlHelp类不理解可以参考：http://blog.csdn.net/yinnan0422/article/details/51691096

如果对SqlCommand用法不理解可以参考：http://blog.csdn.net/jintougao/article/details/8587661

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Data;
using System.Data.Sql;
using System.Data.SqlClient;
using System.Windows.Forms;

namespace WindowsFormsApp3
{
    class SqlHelp
    {
        /// 

        /// DataSource : MY-LAPTOP
        /// Initial Catalog: Test
        /// User ID:
        /// Password:
        /// 
        
        private const string connectionString = @"Data Source=MY-LAPTOP;Initial Catalog=Test;Integrated Security = SSPI";
        
        public SqlHelp() { }

        public static SqlConnection conn;

        //打开数据库连接
        public static void OpenConn()
        {
            string SqlCon = connectionString;//数据库连接字符串
            conn = new SqlConnection(SqlCon);
            if (conn.State==ConnectionState.Closed)
            {
                conn.Open();
            }
        }
        //关闭数据库连接
        public static void CloseConn() {
            if(conn.State.ToString().ToLower() == "open")
            {
                conn.Close();
                conn.Dispose();
            }
        }
        //读取数据
        public static SqlDataReader GetDataReaderValue(string sql) {
            OpenConn();
            SqlCommand cmd = new SqlCommand(sql,conn);
            SqlDataReader dr = cmd.ExecuteReader();
            CloseConn();
            return dr;
        }
        //返回DataSet
        public static DataSet GetDataSetValue(string sql, string tableName) {
            OpenConn();
            SqlDataAdapter da = new SqlDataAdapter(sql,conn);
            DataSet ds = new DataSet();
            da.Fill(ds, tableName);
            CloseConn();
            return ds;
        }
        //返回DataView
        public static DataView GetDataViewValue(string sql) {
            OpenConn();
            SqlDataAdapter da;
            DataSet ds = new DataSet();
            da = new SqlDataAdapter(sql, conn);
            da.Fill(ds, "temp");
            CloseConn();
            return ds.Tables[0].DefaultView;
        }
        //返回DataTable
        public static DataTable GetDataTableValue(string sql) {
            OpenConn();
            SqlDataAdapter da = new SqlDataAdapter(sql,conn);
            DataTable dt = new DataTable();
            da.Fill(dt);
            CloseConn();
            return dt;
        }
        //执行一个Sql操作：添加，删除，更新操作
        public void ExecuteNonQuery(string sql)
        {
            OpenConn();
            SqlCommand cmd;
            cmd = new SqlCommand(sql, conn);
            cmd.ExecuteNonQuery();
            cmd.Dispose();
            CloseConn();
        }
        //执行一个Sql操作：添加，删除，更新操作，返回受影响行数
        public int ExecuteNonQueryCount(string sql)
        {
            OpenConn();
            SqlCommand cmd;
            cmd = new SqlCommand(sql, conn);
            int value = cmd.ExecuteNonQuery();
            return value;
        }
        //执行一条返回第一条记录第一列的SqlCommand命令
        public object ExecuteScalar(string sql)
        {
            OpenConn();
            SqlCommand cmd = new SqlCommand(sql, conn);
            object value = cmd.ExecuteScalar();
            return value;
        }
        //返回记录数
        public int SqlServerRecordCount(string sql)
        {
            OpenConn();
            SqlCommand cmd = new SqlCommand();
            cmd.CommandText = sql;
            cmd.Connection = conn;
            SqlDataReader dr;
            dr = cmd.ExecuteReader();
            int RecordCount = 0;
            while (dr.Read())
            {
                RecordCount++;
            }
            CloseConn();
            return RecordCount;
        }
        //判断是否为数字
        public static bool GetSafeValue(string value)
        {
            if (string.IsNullOrEmpty(value))
            {
                return false;
            }
            foreach (char ch in value)
            {
                if (!char.IsDigit(ch))
                {
                    return false;
                }
            }
            return true;
        }
        
    }
}

如此在Form1的监听器方法中，便可调用以上SqlHelp方法，以便响应登录按钮的触发

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using System.Data.Sql;
using System.Data.SqlClient;

namespace WindowsFormsApp3
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void label2_Click(object sender, EventArgs e)
        {

        }

        private void label1_Click(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {
            string accStr = this.textBox1.Text;
            string pswStr = this.textBox2.Text;
            
            if(accStr == "" || pswStr == "")
            {
                MessageBox.Show("用户名和密码不能为空，请重新输入");
            }
            else
            {
                string selectSql = "select * from Login_Table where Account='" + accStr + "' and Password='"+pswStr+"'";
                SqlHelp sqlHelper = new SqlHelp();
                int count = sqlHelper.SqlServerRecordCount(selectSql);
                if (count > 0)//count大于0说明匹配成功
                {
                    MessageBox.Show("信息验证成功");
                    Form2 form = new Form2();
                    form.Show();
                    this.Hide();
                }
                else {
                    MessageBox.Show("用户名或者密码错误");
                }
            }
        }

        private void button2_Click(object sender, EventArgs e)
        {
            //尚未更新
        }

        private void button3_Click(object sender, EventArgs e)
        {
            Application.ExitThread();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            //还没更新
        }

        private void checkBox1_CheckedChanged(object sender, EventArgs e)
        {
            if (checkBox1.Checked)
            {
                textBox2.PasswordChar = new Char();//当勾选框的时候，为显示密码
            }
            else {
                textBox2.PasswordChar = '*';//当不勾选的时候，为密文状态
            }
        }
    }
}

二、编写主界面Form2

namespace WindowsFormsApp3
{
    partial class Form2
    {
        /// 

        /// Required designer variable.
        /// 
        private System.ComponentModel.IContainer components = null;

        /// 

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

        #region Windows Form Designer generated code

        /// 

        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// 
        private void InitializeComponent()
        {
            this.label1 = new System.Windows.Forms.Label();
            this.button1 = new System.Windows.Forms.Button();
            this.button2 = new System.Windows.Forms.Button();
            this.SuspendLayout();
            // 
            // label1
            // 
            this.label1.AutoSize = true;
            this.label1.Font = new System.Drawing.Font("宋体", 15F);
            this.label1.Location = new System.Drawing.Point(128, 37);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(287, 25);
            this.label1.TabIndex = 0;
            this.label1.Text = "欢迎您，您已经成功登录";
            // 
            // button1
            // 
            this.button1.Font = new System.Drawing.Font("宋体", 13F);
            this.button1.Location = new System.Drawing.Point(133, 116);
            this.button1.Name = "button1";
            this.button1.Size = new System.Drawing.Size(75, 33);
            this.button1.TabIndex = 1;
            this.button1.Text = "确定";
            this.button1.UseVisualStyleBackColor = true;
            this.button1.Click += new System.EventHandler(this.button1_Click);
            // 
            // button2
            // 
            this.button2.Font = new System.Drawing.Font("宋体", 13F);
            this.button2.Location = new System.Drawing.Point(340, 116);
            this.button2.Name = "button2";
            this.button2.Size = new System.Drawing.Size(75, 33);
            this.button2.TabIndex = 2;
            this.button2.Text = "退出";
            this.button2.UseVisualStyleBackColor = true;
            this.button2.Click += new System.EventHandler(this.button2_Click);
            // 
            // Form2
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(8F, 15F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(550, 184);
            this.Controls.Add(this.button2);
            this.Controls.Add(this.button1);
            this.Controls.Add(this.label1);
            this.Name = "Form2";
            this.Text = "Form2";
            this.ResumeLayout(false);
            this.PerformLayout();

        }

        #endregion

        private System.Windows.Forms.Label label1;
        private System.Windows.Forms.Button button1;
        private System.Windows.Forms.Button button2;
    }
}

主界面控件完成后即可，在“登录”按钮操作下，课进入数据库中比对，如果账号密码比对成功，即可进入Form2登录主界面，否则提示错误。