如何使用Dapper为sql语句提供文本框值

Question

两次单击按钮的错误消息为：

附加信息：类型为System.Windows.Controls.TextBox的成员Id不能用作参数值

private void Button_Click(object sender, RoutedEventArgs e)
{
var connection = new SqlConnection(sqlConnectionString);
Student student = new Student();
connection.Open();

var affectedRows = connection.Execute("Delete from Student Where Id = @Id", new { Id = txtStudentID });
connection.Close();
//return affectedRows;
}





private void Button_Click_1(object sender, RoutedEventArgs e)
{
var connection = new SqlConnection(sqlConnectionString);
Student student = new Student();
var affectedRows = connection.Execute("Update Student set Name = @Name, Marks = @Marks Where Id = @Id", new { Id = txtStudentID, Name = txtName.Text, Marks = txtMarks.Text });
connection.Close();
}  

Answer 1

您需要将文本框内的Text作为参数值发送，而不是发送textbox本身

connection.Execute(
"Delete from Student Where Id = @Id", 
new { Id = txtStudentID.Text }
//                       ^^^^^
);

最好不要要求SQL Server进行数据转换。如果数据库中的ID列是整数，则将字符串解析为C#端的整数：

connection.Execute(
"Delete from Student Where Id = @Id", 
new { Id = int.Parse(txtStudentID.Text) }
);

或者使用NumericUpDown控件，这样您就不必担心解析失败(只能输入数字(

connection.Execute(
"Delete from Student Where Id = @Id", 
new { Id = (int)nudStudentID.Value }
);

类似地，如果ID是例如Guid，则解析它。

更新查询也有同样的建议-名称和标记上有.Text(它是数字？请参阅上面的解析建议(，但ID上没有；可能是复制错误

---

其他建议：

您应该编写using var来创建连接。你不需要培养一个新学生。Dapper将打开/关闭已关闭的连接。它将打开由您打开的连接。您不使用受影响的行，因此不需要捕获它：

private void Button_Click_1(object sender, RoutedEventArgs e)
{
using var connection = new SqlConnection(sqlConnectionString);
connection.Execute(
"Update Student set Name = @Name, Marks = @Marks Where Id = @Id", 
new { 
Id = int.Parse(txtStudentID.Text), 
Name = txtName.Text, 
Marks = double.Parse(txtMarks.Text)
}
);
}  

Answer 2

txtStudentID是控件吗？如果是，则应使用txtStudentID的Text属性。如果是数字数据类型，则可以尝试.ToString((it.