如何在 vb.net 数据库中显示消息中的值

Question

如何在 vb.net 数据库中的消息框中显示值？我需要帮助

如果我在文本框中输入了错误的值，我想显示值，然后消息框显示数据库中的原始值。

Dim cmdAB As String
Dim daAB As SqlClient.SqlDataAdapter
Dim dsAB As DataSet
Dim dtAB As DataTable
cmdAB = "SELECT * FROM English_Test WHERE school_code= '" & school_code & "' and child_id= '" & child_id & "' and english_1= '" & English_1TextBox.Text & "'"
daAB = New SqlClient.SqlDataAdapter(cmdAB, cnn)
dtAB = New DataTable()
dsAB = New DataSet()
daAB.Fill(dsAB, "English_Test")
dtAB = dsAB.Tables("English_Test")
If (dtAB.Rows.Count > 0) Then
English_2TextBox.Focus()
Else
MessageBox.Show("English 1: " & dtAB.Rows(0).Item("english_1") & " not found.", "" & Name & " - Not Found", MessageBoxButtons.OK, MessageBoxIcon.Warning)
English_1TextBox.Enabled = True
English_1TextBox.Text = Nothing
English_1TextBox.Focus()
End If

Answer 1

这是您使用参数的方式，也是使用...EndUsing 块可确保即使出现错误，也能正确关闭和处置对象。

Private Sub CheckOriginalData()
Dim Name As String = ""
Dim school_code As String = ""
Dim child_id As String = ""
Dim dtAB As New DataTable
Using cn As New SqlConnection("Your connection string")
Dim cmdAB As String = "SELECT * FROM English_Test WHERE school_code= @SchoolCode and child_id= @ChildID and english_1= @English1;"
Using cmd As New SqlCommand(cmdAB, cn)
cmd.Parameters.Add("@SchoolCode", SqlDbType.VarChar).Value = school_code
cmd.Parameters.Add("@ChildID", SqlDbType.VarChar).Value = child_id
cmd.Parameters.Add("@English1", SqlDbType.VarChar).Value = English_1TextBox.Text
cn.Open()
Using dr As SqlDataReader = cmd.ExecuteReader
dtAB.Load(dr)
End Using
End Using
End Using
If (dtAB.Rows.Count > 0) Then
English_2TextBox.Focus()
Else
MessageBox.Show("English 1: " & English_1TextBox.Text & " not found.", Name & " - Not Found", MessageBoxButtons.OK, MessageBoxIcon.Warning)
English_1TextBox.Enabled = True
English_1TextBox.Text = Nothing
English_1TextBox.Focus()
End If
End Sub

最后，你的问题。如果你的数据表没有行，那么引用一行和一列来获取值是行不通的。您提供了该值，但它仍在文本框中，而不是数据库中。请记住，它没有找到。