Question

我已经尝试了一段时间了，所以在我的MS访问数据库中我有一个

Table named "reservations"  and inside the table are
Name(sid,jen)
Roomtype(single,double)
Arrivaldate(3/20/17,  3/20/17 )
Departuredate(3/21/17, 3/21/17)

在我的视觉工作室形式中我有

2 labels = lblsingle , lbldouble
1 button  named btnok and
Datetimepicker named Datetimepicker1 (properties format set to "Short")

所以这是我的代码：

Private sub Form1_Load

Dim time as DateTime = DateTime.Now
Dim format As String = "MM/d/yyyy"
Datetimepicker1.Text = time.ToString(format)

Private sub btnok_click

Con.open

Dim cmb As new OleDbCommand("SELECT COUNT (*) FROM [reservations] WHERE [Roomtype] = 'Single' AND  [Arrivaldate] = " & Datetimepicker1.Text & " ",Con)
Dim dr As OleDbDataReader = cmb.ExecuteReader
Dim userfound As Boolean = False

While dr.Read
    userfound = True
    lblsingle.text = (dr(0).ToString())
End While
Con.Close()
End Sub
End Class

。所以我想要发生的是当我在datetimepicker1中选择日期3/20/17时。我的lblsingle.text应该计入＆＃34; 1＆＃34;因为在我的数据库中有一个与datetkmepicker1具有相同日期的单个数据库。但结果是＆＃34; 0＆＃34; .........我真的觉得有些东西让我的datetimepicker1和我的ms中的日期访问不同，请帮助....我需要在某处更改时间格式吗？

Answer 1

首先，您的“Private sub btnok_click”将无法处理按钮点击。

要处理“按钮点击”，您的实现应如下所示（proto）：

Private Sub button1_Click(sender As Object, e As System.EventArgs) Handles button1.Click
..
..
..
..
End Sub.

来到业务逻辑：

如果要更新/增加标签？

根据您问题中的描述，您希望在“DatTimePicker”值更改后立即更新/增加标签。

但是在代码中，您正尝试在“确定”按钮单击中执行此操作。

如果您想更新标签，当您从“datetimepicker”中选择日期时，请处理以下事件（proto）：

Private Sub DateTimePicker1_ValueChanged(sender as Object, e as EventArgs) _ 
     Handles DateTimePicker1.ValueChanged

..
..
..
..

End Sub

Answer 2

您必须将日期作为日期时间处理，而不是文本：

Dim time as DateTime = DateTime.Today
Dim format As String = "yyyy'/'MM'/'/dd"

Datetimepicker1.Value = time

Private sub btnok_click

Con.open

Dim cmb As new OleDbCommand("SELECT COUNT (*) FROM [reservations] WHERE [Roomtype] = 'Single' AND  [Arrivaldate] = #" & time.ToString(format) & "# ",Con)

Answer 3

不使用日期和时间的文字表示形式 - 将DateTime用于除用户的渲染输出之外的所有目的（或序列化为CSV文件等文本输出）。

处理控件的DateTime值

使用.Value属性来获取和设置控件值：

Datetimepicker1.Value = DateTime.Now

处理数据库查询的DateTime值

使用（typed）参数将DateTime值传递给数据库查询：

Dim cmb As new OleDbCommand("SELECT COUNT (*) FROM [reservations] WHERE [Roomtype] = 'Single' AND [Arrivaldate] = ?", Con)
cmb.Parameters.Add(Datetimepicker1.Value)

OleDbCommand使用位置参数 - 这意味着您需要在添加参数时匹配占位符的顺序：

Dim roomtype As String
roomtype = "Single"

Dim cmb As new OleDbCommand("SELECT COUNT (*) FROM [reservations] WHERE [Roomtype] = ? AND [Arrivaldate] = ?", Con)
cmb.Parameters.Add(roomtype)
cmb.Parameters.Add(Datetimepicker1.Value)

简化检索标量结果，如count（*）

如果您尝试获取的只是count(*)，则不需要OleDbDataReader - 让您的命令ExecuteScalar

lblsingle.Text = cmb.ExecuteScalar()

计数客人预订视觉工作室Ms访问

3 个答案: