我在运行时使用 Tabcontrol 创建的所有标签页无法显示第三个按钮，即使我的数据库中有它

Question

Why all my tabpage created during tuntime using Tabcontrol can't show my 3rd button even it is there in my database? It's like it being limted to show 2 button only but i checked every code in my program, nothing is limiting everythings is ".count - 1"

Imports System.Data.OleDb

Public Class Services

Dim con = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source = Cypher.mdb;"
Dim cnnOledb As New OleDbConnection
Dim cmdload As New OleDbCommand
Dim cmdInsert As New OleDbCommand
Public categoryName As String

Private Sub Services_Load(sender As Object, e As EventArgs) Handles MyBase.Load

    Me.CenterToScreen()
    cnnOledb.ConnectionString = con
    cnnOledb.Open()
    cmdload.CommandText = "Select * From [Services]"
    cmdload.Connection = cnnOledb
    Max()
    Tab()
    add_btn()

End Sub

Private Sub Max()
    Dim cmdMax As New OleDbCommand
    cmdMax.CommandText = "Select MAX(id) from Services"
    cmdMax.Connection = cnnOledb
    Try
        Dim dr As OleDbDataReader = cmdMax.ExecuteReader()
        If dr.Read = True Then
            If dr(0).ToString = "" Then
                txtID.Text = "1"
            Else
                txtID.Text = dr(0) + 1.ToString
            End If
        End If
    Catch
        MsgBox("Error !")
    End Try

End Sub


Private Sub Tab()
    cobCategory.Items.Clear()
    TabCategory.TabPages.Clear()

    Dim cmdCategory As New OleDbCommand
    cmdCategory.CommandText = "Select * from Category"
    cmdCategory.Connection = cnnOledb

    Dim dt As New DataTable
    dt.Load(cmdCategory.ExecuteReader)
    For i As Integer = 0 To dt.Rows.Count - 1
        Dim tab As New TabPage()
        tab.Name = "tab" + dt.Rows(i).Item(1).ToString
        tab.Text = tab.Name.Remove(0, 3)
        cobCategory.Items.Add(dt.Rows(i).Item(1).ToString)
        TabCategory.TabPages.Add(tab)
    Next

    TabCategory.TabPages.Add("+")
End Sub

Private Sub add_btn()
    Dim dt As New DataTable
    dt.Load(cmdload.ExecuteReader)

    Dim myFont As System.Drawing.Font

    myFont = New System.Drawing.Font("Century Gothic", 12)

    For i As Integer = 0 To dt.Rows.Count - 1

        Dim btn As New Button()
        btn.Name = "btn" + dt.Rows(i).Item(2).ToString
        btn.Text = btn.Name.Remove(0, 3)
        btn.Height = 30
        btn.Width = 90
        btn.Location = New Point(0, 10)
        If TabCategory.TabPages((dt.Rows(i).Item(1)) - 1).Controls.count <> 0 Then
            btn.Left += 100
        End If
        btn.Font = myFont

        TabCategory.TabPages((dt.Rows(i).Item(1)) - 1).Controls.Add(btn)
    Next

End Sub

Private Sub btnAdd_Click(sender As Object, e As EventArgs) Handles btnAdd.Click
    Try
        cmdInsert.CommandText = "Insert into [Services] values(" & txtID.Text & ", " & cobCategory.SelectedIndex + 1 & ", '" & txtServices.Text & "',  " & txtDur.Text & ", " & txtPrices.Text & ");"
        cmdInsert.CommandType = CommandType.Text
        cmdInsert.Connection = cnnOledb
        cmdInsert.ExecuteNonQuery()
    Catch ex As Exception
        MsgBox("Fail to insert data")
    End Try
End Sub

Private Sub TabCategory_Click(sender As Object, e As EventArgs) Handles TabCategory.Click
    If TabCategory.SelectedTab Is TabCategory.TabPages(TabCategory.TabPages.Count - 1) Then
        New_Category.ShowDialog()
    End If
End Sub

Public Sub New_Cate()
    Dim cmdMax As New OleDbCommand
    cmdMax.CommandText = "Select MAX(ID) from Category"
    cmdMax.Connection = cnnOledb
    Dim ID As Integer
    Try
        Dim dr As OleDbDataReader = cmdMax.ExecuteReader()
        If dr.Read = True Then
            If dr(0).ToString = "" Then
                ID = 1
            Else
                ID = dr(0) + 1
            End If
        End If
    Catch
        MsgBox("Error !")
    End Try

    Dim cmdAddCategory As New OleDbCommand
    Try
        cmdAddCategory.CommandText = "Insert into [Category] values(" & ID & ", '" & categoryName & "');"
        cmdAddCategory.CommandType = CommandType.Text
        cmdAddCategory.Connection = cnnOledb
        cmdAddCategory.ExecuteNonQuery()
    Catch ex As Exception
        MsgBox("Fail to insert new category")
    End Try

    Tab()
End Sub
End Class

Answer 1

按钮在那里，在第二个按钮的后面。您的代码最初将按钮放置在 x = 0 处，然后当 Tabpage.controls.count > 0 时，它会添加 100。因此第一个按钮之后的每个按钮都位于 x = 100.

改变这个：

   btn.Location = New Point(0, 10)
   If TabCategory.TabPages((dt.Rows(i).Item(1)) - 1).Controls.count <> 0 Then
        btn.Left += 100
   End If

最后一个按钮右边+100:

   btn.Location = New Point(0, 10)
   If TabCategory.TabPages((dt.Rows(i).Item(1)) - 1).Controls.count <> 0 Then
        btn.Left += TabCategory.TabPages((dt.Rows(i).Item(1)) - 1).Controls(TabCategory.TabPages((dt.Rows(i).Item(1)) - 1).Controls.Count - 1).Left + 100
   End If

我在运行时使用 Tabcontrol 创建的所有标签页无法显示第三个按钮，即使我的数据库中有它

All my tabpage create in runtime using Tabcontrol can't show 3rd button even i have it in my database

sql

vb.net

oledb

tabcontrol

tabpage