1. 新建数据库TestDB，新建表UserInfo，如下图：

   
   
   UserInfo表的设计.png

2.创建WinForm项目

第一步：在App.config中添加数据库连接字符串：

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <connectionStrings>
    <add name="SqlConn" connectionString="server=.;uid=sa;pwd=xxxxxx;database=TestDB"/>
  </connectionStrings>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2" />
    </startup>
</configuration>

第二步：创建静态类SqlHelper，用于返回连接字符串

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace UserInfoManagerMyPractice
{
    class SqlHelper
    {
        public static string GetSqlConnectionString()
        {
            return ConfigurationManager.ConnectionStrings["SqlConn"].ConnectionString;
        }
    }
}

第三步：根据UserInfo表，创建对应的UserInfo类：

    class UserInfo
    {
        public int UserId { get; set; }
        public string UserName { get; set; }
        public int UserAge { get; set; }
        public DateTime createdDate { get; set; }
        public string UserPwd { get; set; }
        public DateTime LastErrorDateTime { get; set; }
        public int ErrorTimes { get; set; }
        public int DelFlg { get; set; }
    }

第四步：在主窗口上添加一个DataGridView和一个Button：

主窗口设计.png

第五步：添加主窗口载入时的处理：

        private void Form1_Load(object sender, EventArgs e)
        {
            LoadUserInfos();
        }

        private void LoadUserInfos()
        {
            string connStr = SqlHelper.GetSqlConnectionString();
            // 把读取到的数据转换成类并存入List中，作为DataGridView的数据源
            List<UserInfo> userInfoList = new List<UserInfo>();
            using (SqlConnection conn = new SqlConnection(connStr))
            {
                conn.Open();
                using(SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = @"SELECT [UserId]
                                              ,[UserName]
                                              ,[UserAge]
                                              ,[CreatedDate]
                                              ,[UserPwd]
                                              ,[LastErrorDateTime]
                                              ,[ErrorTimes]
                                              ,[DelFlag]
                                          FROM [TestDB].[dbo].[UserInfo]";
                    using (SqlDataReader reader = cmd.ExecuteReader())
                    {
                        while (reader.Read())
                        {
                            UserInfo user = new UserInfo();
                            user.UserId = int.Parse(reader["UserId"].ToString());
                            user.UserName = reader["UserName"] == DBNull.Value ? string.Empty : reader["UserName"].ToString();
                            user.UserAge = int.Parse(reader["UserAge"].ToString());
                            user.createdDate = DateTime.Parse(reader["CreatedDate"].ToString());
                            user.UserPwd = reader["UserPwd"].ToString();
                            user.LastErrorDateTime = DateTime.Parse(reader["LastErrorDateTime"].ToString());
                            user.ErrorTimes = int.Parse(reader["ErrorTimes"].ToString());
                            user.DelFlg = int.Parse(reader["DelFlag"].ToString());
                            userInfoList.Add(user);
                        }
                    }
                }
            }
            this.dataGridView1.DataSource = userInfoList;
        }

运行程序，效果如下图：

运行效果.png

第六步：实现点击“软”删除一列，并点击保存按钮后生效：

根据DelFlg字段中的值，确定该行数据是否已被删除

 private void button1_Click(object sender, EventArgs e)
        {
            // 首先获得当前用户所选择的行
            var rows = this.dataGridView1.SelectedRows;
            if (rows.Count <= 0)
            {
                MessageBox.Show("请选择要删除的行");
            }
            StringBuilder sqlSb = new StringBuilder();
            List<SqlParameter> parameters = new List<SqlParameter>();
            for (int i = 0; i < rows.Count; i++)
            {
                sqlSb.Append("update UserInfo set DelFlag=1 where UserId=@UserId" + i + ";");
                SqlParameter parameter = new SqlParameter(@"UserId" + i, SqlDbType.Int);
                parameter.Value = int.Parse(rows[i].Cells["UserId"].Value.ToString());
                parameters.Add(parameter);
            }
            // 根据主键进行“删除”操作
            using (SqlConnection conn = new SqlConnection(SqlHelper.GetSqlConnectionString()))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = sqlSb.ToString();
                    cmd.Parameters.AddRange(parameters.ToArray());
                    cmd.ExecuteNonQuery();
                    // 刷新数据显示
                    LoadUserInfos();
                }
            }
        }

执行效果.png

另：
1.使用SqlDataAdapter的方法如下：

   #region 查询按钮功能的实现
        private void SearchButton_Click(object sender, EventArgs e)
        {
            string connStr = SQLHelper.GetSqlConnectionString();
            string sqlText = @"SELECT [AddressID]
                                      ,[AddressLine1]
                                      ,[City]
                                      ,[StateProvince]
                                      ,[CountryRegion]
                                      ,[PostalCode]
                                      ,[ModifiedDate]
                                  FROM [AdventureWorksLT2008R2].[SalesLT].[Address]";
            List<string> whereList = new List<string>();
            List<SqlParameter> parameters = new List<SqlParameter>();
            if (!string.IsNullOrEmpty(this.StateProvinceTXT.Text.Trim()))
            {
                whereList.Add(" StateProvince like @StateProvince ");
                SqlParameter parameter = new SqlParameter();
                parameter.ParameterName = "@StateProvince";
                parameter.Value = "%" + this.StateProvinceTXT.Text + "%";
                parameters.Add(parameter);
            }
            if (!string.IsNullOrEmpty(this.AddressTXT.Text.Trim()))
            {
                whereList.Add(" AddressLine1 like @AddressLine1 ");
                SqlParameter parameter = new SqlParameter();
                parameter.ParameterName = "@AddressLine1";
                parameter.Value = "%" + this.AddressTXT.Text + "%";
                parameters.Add(parameter);
            }
            if (whereList.Count > 0)
            {
                sqlText += " WHERE " + string.Join(" and ", whereList);
            }

            
            List<Address> addressList = new List<Address>();
            using (SqlDataAdapter adapter = new SqlDataAdapter(sqlText, SQLHelper.GetSqlConnectionString()))
            {
                adapter.SelectCommand.Parameters.AddRange(parameters.ToArray());
                DataTable dt = new DataTable();
                adapter.Fill(dt);

                foreach (DataRow dataRow in dt.Rows)
                {
                    Address address = new Address();
                    address.AddressLine = dataRow["AddressLine1"].ToString();
                    address.City = dataRow["City"].ToString();
                    address.StateProvince = dataRow["StateProvince"].ToString();
                    address.CountryRegion = dataRow["CountryRegion"].ToString();
                    address.PostalCode = dataRow["PostalCode"].ToString();
                    address.ModifiedDate = DateTime.Parse(dataRow["ModifiedDate"].ToString( ));
                    addressList.Add(address);
                }
                this.AddressGridView.DataSource = addressList;
            }
        }
        #endregion

2.使用SqlDataReader的方法：

 #region 双击GridView中一列的处理方法
        private void AddressGridView_DoubleClick(object sender, EventArgs e)
        {
            if (this.AddressGridView.SelectedRows.Count <= 0)
            {
                return;
            }
            int selectedRowID = int.Parse(this.AddressGridView.SelectedRows[0].Cells[0].Value.ToString());
            using (SqlConnection conn = new SqlConnection(SQLHelper.GetSqlConnectionString()))
            {
                conn.Open();
                using (SqlCommand cmd = conn.CreateCommand())
                {
                    cmd.CommandText = @"SELECT [AddressID]
                                              ,[AddressLine1]
                                              ,[City]
                                              ,[StateProvince]
                                              ,[CountryRegion]
                                              ,[PostalCode]
                                              ,[ModifiedDate]
                                          FROM [AdventureWorksLT2008R2].[SalesLT].[Address] WHERE [AddressID]=@AddressID";
                    SqlParameter parameter = new SqlParameter();
                    parameter.ParameterName = "@AddressID";
                    parameter.Value = selectedRowID;
                    cmd.Parameters.Add(parameter);
                    using (SqlDataReader reader = cmd.ExecuteReader())
                    {
                        Address address = new Address();
                        if (reader.Read())
                        {
                            address.AddressID = int.Parse(reader["AddressID"].ToString());
                            address.AddressLine = reader["AddressLine1"].ToString();
                            address.City = reader["City"].ToString();
                            address.StateProvince = reader["StateProvince"].ToString();
                            address.CountryRegion = reader["CountryRegion"].ToString();
                            address.PostalCode = reader["PostalCode"].ToString();
                            address.ModifiedDate = DateTime.Parse(reader["ModifiedDate"].ToString());
                        }
                        this.AddressIDTXT.Text = address.AddressID.ToString();
                        this.AddressTXT.Text = address.AddressLine;
                        this.CityTXT.Text = address.City;
                        this.StateProvinceTXT.Text = address.StateProvince;
                        this.CountryRegionTXT.Text = address.CountryRegion;
                        this.PostalTXT.Text = address.PostalCode;
                        this.ModifiedDateTXT.Text = address.ModifiedDate.ToShortDateString();
                    }

                }
            }
        }
        #endregion