从组合框设置的数据库中检索数据到文本框

Posted 2023-03-29

【中文标题】从组合框设置的数据库中检索数据到文本框

【英文标题】：Retrieve data from database set by combobox to textbox

【发布时间】：2013-12-13 06:59:37

【问题描述】：

我有一个表单，它有 1 个组合框和 1 个文本框。

还有一个名为 tbl_dress 的表，其中包含 Dress_ID、Dress_Name、Dress_Price 等列。

组合框显示 Dress_Name 并且代码有效..

组合框代码：-

Private Sub FillCombo()
        Try
            Dim fillcon As New OleDb.OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\annonymous\Documents\Visual Studio 2012\Projects\DressTest\DressTest\db\PriceTesting.accdb")
            Dim query As String = ("SELECT Dress_Name FROM tbl_dress")
            Dim da As New OleDb.OleDbDataAdapter(query, fillcon)
            Dim ds As New DataSet
            da.Fill(ds)
            ComboBox1.ValueMember = "Dress_Name"
            ComboBox1.DataSource = ds.Tables(0)
            ComboBox1.SelectedIndex = 0
        Catch ex As Exception
            MsgBox("ERROR : " & ex.Message.ToString)
        End Try
    End Sub

这是加载我的表单时的代码：-

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        Try
            Dim con As New OleDb.OleDbConnection
            con.ConnectionString = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\annonymous\Documents\Visual Studio 2012\Projects\TMS Final\TMS Final\db\db_TMS.accdb"
            con.Open()

            FillCombo() ' Display data from tbl_order on form load
            con.Close()
        Catch ex As Exception
            MessageBox.Show(ex.ToString)
        End Try

    End Sub

所以问题是，我如何获得 Dress_Price ，由组合框中选择的 Dress_Name 决定。

我已尝试以下代码，但出现错误。

Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged 
Try 
    Dim fillcon As New OleDb.OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\annonymous\Documents\Visual Studio 2012\Projects\DressTest\DressTest\db\PriceTesting.accdb") 

    fillcon.Open() 

    Dim query As String = ("SELECT Dress_Price FROM tbl_dress WHERE Dress_Name = ' " & ComboBox1.SelectedValue.ToString & " ' ") 
    Dim cmd As New OleDb.OleDbCommand(query, fillcon) 
    cmd.CommandText = query 

    TextBox1.Text = cmd.ExecuteScalar().ToString() 

    fillcon.Close() 

    Catch ex As Exception 
        MessageBox.Show(ex.ToString) 
    End Try 

End Sub

那么我哪里出错了，我该怎么办？ vb.net 新手

【参考方案1】：

在执行时试试这一行

TextBox1.Text=Convert.ToInt32(cmd.ExecuteScalar()).ToString()

【参考方案2】：

我的问题是你是否在那个时候获得了想要的价值

你能把塞子放在下面的方法附近看看返回值吗

Dim query As String = ("SELECT Dress_Price FROM tbl_dress WHERE Dress_Name = ' " & ComboBox1.SelectedValue.ToString & " ' ")

尝试硬编码礼服名称并检查。也可以试试 Select Top 1

【讨论】：

在代码行打断点，查看query的值

或硬编码您的查询，即 Dim query As String = ("SELECT Dress_Price FROM tbl_dress WHERE Dress_Name =SomeDressName") 并查看您是否得到想要的结果

在我的表中.. 我指定 Dress_Name 是 Tuxedo 、 Dress 和 Bikini ，而 Dress_Price 分别是 200 、 150 、 50 .. 但代码没有返回确切的值..跨度>

你可以试试这行 Dim query As String = ("SELECT Dress_Price FROM tbl_dress WHERE Dress_Name =Bikini ") 以及 TextBox1.Text= Convert.ToDouble(cmd.ExecuteScalar()).ToString()

试试这个 Dim 查询 As String = ("SELECT Dress_Price FROM tbl_dress WHERE Dress_Name =[Bikini]")

【参考方案3】：

Private Sub ComboBox1_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox1.SelectedIndexChanged 
    Try 
        Dim fillcon As New OleDb.OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=C:\Users\annonymous\Documents\Visual Studio 2012\Projects\DressTest\DressTest\db\PriceTesting.accdb") 

        fillcon.Open() 

        Dim query As String = ("SELECT Dress_Price FROM tbl_dress WHERE Dress_Name = ' " & ComboBox1.Text & " ' ") 
        Dim cmd As New OleDb.OleDbCommand(query, fillcon) 
        cmd.CommandText = query 

        TextBox1.Text = cmd.ExecuteScalar().ToString() 

        fillcon.Close() 

    Catch ex As Exception 
        MessageBox.Show(ex.ToString) 
    End Try 

End Sub