我已经声明了 2 个字符串变量:
string fname;
string lname;
当我在 phpMyAdmin 数据库中编写 MySQL 查询时:
SELECT workers.FNAME, workers.LNAME FROM project1.workers INNER JOIN
project1.order_status ON workers.ID_WORKER = order_status.ID_WORKER
INNER JOIN project1.orders ON orders.ID_ORDER = order_status.ID_ORDER
WHERE orders.ORDER_NUMBER = 'TEST' GROUP BY workers.FNAME, workers.LNAME
我有 2 个工作人员:
-“亚当盖克斯”和
“安德鲁蠕虫”
然后我想存储来自这个查询的对象并将该数据加载到 datagridview:
string query1 = string.Format("SELECT workers.FNAME, workers.LNAME FROM project1.workers INNER JOIN project1.order_status " +
"ON workers.ID_WORKER = order_status.ID_WORKER INNER JOIN project1.orders ON orders.ID_ORDER = order_status.ID_ORDER " +
"WHERE orders.ORDER_NUMBER = '"+ NrOrder +"' GROUP BY workers.FNAME, workers.LNAME");
SQLdata.connection.Open();
using (var command = new MySqlCommand(query1, SQLdata.connection))
{
using (var reader1 = command.ExecuteReader())
{
while (reader1.Read())
{
fname = Convert.ToString(reader1[0]);
lname = Convert.ToString(reader1[1]);
}
}
}
我在 while 循环中的代码行中设置了断点,并读取了所有 FNAME 和 LNAME。然后它正确加载所有数据。接下来我想将它们加载到 datagridview。
SQLdata.connection.Close();
sick_leaves x = new sick_leaves();
x.FNAME = fname;
x.LNAME = lname;
return x;
并像这样绑定(bind)它们:
sick_leaves a = calculate_sickness_leaves(txt_NrOrder.Text);
cu = calculate_sickness_leaves(txt_NrOrder.Text);
var source = new BindingSource();
source.DataSource = cu;
dataGridView2.DataSource = source;
然后使用 Orders.cs 文件中的数据:
public class sick_leaves
{
public string FNAME { get; set; }
public string LNAME { get; set; }
}
在 datagridview 中编译后,我只加载了 1 个 Worker:“Andrew Worm”。那应该是那 2 个工作人员,所以它没有从 sql 查询加载所有数据。
现在:如何将所有数据从 sql 查询加载到 datagridview?有任何想法吗? 警告!我需要桌面应用程序方面的帮助
编辑
我想通过保存代码结构来加载该数据,因为我想通过计算疾病来构建数据 GridView ,留下时间。 (使用 TimeSpan
对象)。这样写可以吗?
我的代码:
GenerateOrder.cs:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;
using MySql.Data.MySqlClient;
using System.Windows.Forms.DataVisualization.Charting;
using iTextSharp.text;
using iTextSharp.text.pdf;
using System.IO;
using System.Diagnostics;
namespace ControlDataBase
{
public partial class GenerateChartsOfOrders : Form
{
string fname;
string lname;
sick_leaves cu = new sick_leaves();
public GenerateChartsOfOrders()
{
InitializeComponent();
}
public void loaddata2()
{
string connect = "datasource=localhost;port=3306;username=root;password=";
MySqlConnection connection = new MySqlConnection(connect);
connection.Open();
sick_leaves a = calculate_sickness_leaves(txt_NrOrder.Text);
cu = calculate_sickness_leaves(txt_NrOrder.Text);
var source = new BindingSource();
source.DataSource = cu;
dataGridView2.DataSource = source;
connection.Close();
}
private sick_leaves calculate_sickness_leaves(string NrOrder)
{
string query1 = string.Format("SELECT workers.FNAME, workers.LNAME FROM project1.workers INNER JOIN project1.order_status " +
"ON workers.ID_WORKER = order_status.ID_WORKER INNER JOIN project1.orders ON orders.ID_ORDER = order_status.ID_ORDER " +
"WHERE orders.ORDER_NUMBER = '"+ NrOrder +"' GROUP BY workers.FNAME, workers.LNAME");
SQLdata.connection.Open();
using (var command = new MySqlCommand(query1, SQLdata.connection))
{
using (var reader1 = command.ExecuteReader())
{
while (reader1.Read())
{
fname = Convert.ToString(reader1[0]);
lname = Convert.ToString(reader1[1]);
}
}
}
SQLdata.connection.Close();
sick_leaves x = new sick_leaves();
x.FNAME = fname;
x.LNAME = lname;
return x;
}
}
}
Orders.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
namespace ControlDataBase
{
public class sick_leaves
{
public string FNAME { get; set; }
public string LNAME { get; set; }
}
}
SQLData.cs
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using MySql;
using MySql.Data.MySqlClient;
namespace ControlDataBase
{
class SQLdata
{
public static MySqlConnection connection = new MySqlConnection
("datasource=localhost;port=3306;username=root;password=");
}
}
最佳答案
代码中有几个问题:
- 您已经定义了
fname
和lname
作为表单的字段。 - 在
calculate_sickness_leaves
您在while(reader1.Read())
中设置这些字段的值 - 最后返回一个
sick_leaves
来自calculate_sickness_leaves
的对象.
所以基本上,fname
和 lname
由于1和2。
你的 DataGridView
将始终显示单个记录,因为 3.
解决问题:
- 删除
fname
和lname
因为你不需要它们。 - 更改
calculate_sickness_leaves
的输出类型至IEnumerable<sick_leaves>
. - 在 while 循环中,当从数据读取器读取字段值时,创建一个新实例
sick_leaves
yield 返回它。
旁注
- 始终使用参数化查询来防止 SQL 注入(inject)。
- 始终使用
using
使用连接等一次性对象时的声明。 - 如果您有兴趣使用类型化实体对象,那么您可能想看看 MySQL Connector对于 Entity Framework .
示例
你可以找到很多关于加载数据到DataTable
的例子或使用 DataReader
.不管怎样,我将在这里再分享两个示例,向您展示如何从 MySql 获取数据并将其转换为特定类型的列表。
在以下示例中,我假设您有一个 Employee
像这样上课:
public class Employee
{
public string FirstName { get; set; }
public string LastName { get; set; }
}
示例 1 - 使用 DataAdapter、DataTable 和 Select 扩展方法
public IEnumerable<Employee> GetEmployees()
{
string connectionString = "CONNECTION STRING";
string commandText = "COMMAND TEXT";
DataTable table = new DataTable();
using (var adapter = new MySqlDataAdapter(commandText , connectionString))
adapter.Fill(table);
return table.AsEnumerable().Select(x => new Employee()
{
FirstName = x.Field<string>("FirstName"),
LastName = x.Field<string>("LastName")
});
}
示例 2 - 使用 DataReader 和 yield return new Employee
public IEnumerable<Employee> GetEmployees()
{
string connectionString = "CONNECTION STRING";
string commandText = "COMMAND TEXT";
using (var connection = new MySqlConnection(connectionString))
{
connection.Open();
using (var command = new MySqlCommand(commandText, connection))
{
using (var reader = command.ExecuteReader())
{
while (reader.Read())
{
yield return new Employee()
{
FirstName = reader.GetFieldValue<string>(0),
LastName = reader.GetFieldValue<string>(1)
};
}
}
}
}
}
您可以像这样使用上述任一方法:
bindingSource.DataSource = GetEmployees();
dataGridView.DataSource = bindingSource;
关于c# - 如何将数据从sql查询加载到datagridview?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/57107064/