SqlHelper的编写

1.首先创建一个SqlHelper类
2.在SqlHelper下创建连接字符串,首先在获取连接字符串的内容，把它写到配置文件的Configuration的ConnectionString下，并命名为mssqlserver：

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5.2" />
    </startup>
  <connectionStrings>
    <add name="mssqlserver" connectionString="Data Source=.;Initial Catalog=BIO;Integrated Security=True"/>
  </connectionStrings>
</configuration>

然后通过ConfigurationManager.ConnectionStrings方法提取连接字符串：

 private static readonly string conStr = ConfigurationManager.ConnectionStrings["mssqlserver"].ConnectionString;

3. 封装ExcuteNonQuery方法

public static int ExcuteNonQuery(string sql,CommandType cmdType,params SqlParameter[] pms)
        {
            using (SqlConnection conn=new SqlConnection(conStr))
            {
                using (SqlCommand cmd=new SqlCommand(sql,conn))
                {
                    cmd.CommandType = cmdType;
                    if (pms !=null)
                    {
                        cmd.Parameters.AddRange(pms);
                    }
                    conn.Open();
                    return cmd.ExecuteNonQuery();
                }
            }
        }

4.封装ExcuteScalar方法

public static object ExcuteScalar(string sql, CommandType cmdType, params SqlParameter[] pms)
        {
            using (SqlConnection conn = new SqlConnection(conStr))
            {
                using (SqlCommand cmd = new SqlCommand(sql, conn))
                {
                    cmd.CommandType = cmdType;
                    if (pms!=null)
                    {
                        cmd.Parameters.AddRange(pms);
                    }
                    conn.Open();
                    return cmd.ExecuteScalar();
                }
            }
        }

5.封装ExcuteReader方法

        public static SqlDataReader ExcuteReader(string sql, CommandType cmdType, params SqlParameter[] pms)
        {
            SqlConnection conn = new SqlConnection(conStr);

            using (SqlCommand cmd = new SqlCommand(sql, conn))
            {
                if (pms !=null)
                {
                    cmd.Parameters.AddRange(pms);
                }

                cmd.CommandType = cmdType;
                try
                {
                    conn.Open();
                    return cmd.ExecuteReader(CommandBehavior.CloseConnection);
                }
                catch
                {
                    conn.Close();
                    conn.Dispose();
                    throw;
                }
            }
            
        }