Question

好的，所以这是我第一次尝试使用手动数据库表单而且我失败了...我不能为我的生活弄清楚为什么它没有填充网格视图或文本框。我有一个构建数据集的数据类，在Form Class中是控件的填充位置。

你能告诉我我做错了什么吗？我是数据库应用程序的菜鸟。

这是我的数据类：

Option Strict Off
Option Explicit On

Imports System.Data

Public Class DataClass

Private CategoriesProductsDataSet As NORTHWNDDataSet


'Table adapters for product form
Private CategoriesTableAdapter As NORTHWNDDataSetTableAdapters.CategoriesTableAdapter
Private ProductTableAdapter As NORTHWNDDataSetTableAdapters.ProductsTableAdapter


'Declare data relation for the product form
Private CategoriesToProducts As DataRelation


'================================================================
'Create constructor for class
Public Sub New()

    Try
        With Me

            'Instantiate the data sets
            .CategoriesProductsDataSet = New NORTHWNDDataSet

            'Instantiate the table adapters 
            .ProductTableAdapter = _
                New NORTHWNDDataSetTableAdapters.ProductsTableAdapter
            .CategoriesTableAdapter = _
                New NORTHWNDDataSetTableAdapters.CategoriesTableAdapter


            'Assign the products data relation to the dataset
            .CategoriesToProducts = CategoriesProductsDataSet.Relations!CategoriesToProducts


            'Fill the dataset using the fill method of the table adapters
            .ProductTableAdapter.Fill(.CategoriesProductsDataSet.Products)
            .CategoriesTableAdapter.Fill(.CategoriesProductsDataSet.Categories)


        End With

    Catch ex As Exception
        MessageBox.Show("Error in data class", "error", MessageBoxButtons.OK)

    End Try

End Sub

'================================================================

Public Function GetCategoriesProductsDataSet() As NORTHWNDDataSet

    'Return the data set
    Return CategoriesProductsDataSet

End Function

这是产品表格：

Option Strict Off
Option Explicit On

Imports System.Data

'Module: ProductForm
'Abstract:      This form displays all product information from the database 
'for the employee to edit or add to.


Public Class ProductForm


'Declare module-level variables
Private CategoriesProductsData As DataClass
Private CategoriesProductsDataSet As NORTHWNDDataSet

Private CategoriesTableAdapter As  _
    NORTHWNDDataSetTableAdapters.ProductsTableAdapter
Private ProductsTableAdapter As  _
    NORTHWNDDataSetTableAdapters.CategoriesTableAdapter

这两行被注释掉了，因为它告诉我已经为这两个绑定源创建了Friends WithEvents。虽然我找不到它们。

'Private WithEvents ProductsBindingSource As BindingSource
'Private WithEvents CategoriesBindingSource As BindingSource

Private AddingBoolean As Boolean
Private ClosingBoolean As Boolean
Private EditingBoolean As Boolean

Private GridInitializedBoolean As Boolean
Private CategoryIDString As String   'holds the category id to filter the data

'===============================================================
Private Sub ProductForm_Load(ByVal sender As Object, _
        ByVal e As System.EventArgs) Handles Me.Load

这段代码产生了错误：

    Try
        CategoriesProductsData = New DataClass
        CategoriesProductsDataSet = New NORTHWNDDataSet

        CategoriesProductsDataSet = _
            CategoriesProductsData.GetCategoriesProductsDataSet

        'Set up binding sources
        ProductsBindingSource = New BindingSource
        CategoriesBindingSource = New BindingSource

        'Set the data source and data member
        With CategoriesBindingSource
            .DataSource = CategoriesProductsDataSet
            .DataMember = "Products"
            .Sort = "CategoryID"
        End With

        With ProductsBindingSource
            .DataSource = CategoriesBindingSource
            .DataMember = "ProductsToCategories"
        End With


    Catch ex As Exception
        MessageBox.Show("Database Error", "Error", MessageBoxButtons.OK)

    End Try

它会抛出我的消息框，所以我假设它没有正确连接到数据库。

    'Establish record count
    CategoriesBindingSource.MoveLast()
    CategoriesBindingSource.MoveFirst()

    'Bind the textboxes
    CategoryIDTextBox.DataBindings.Add("text", _
                    CategoriesBindingSource, "CategoryID")
    CategoryNameTextBox.DataBindings.Add("text", _
                    CategoriesBindingSource, "CategoryName")
    DescripRichTextBox.DataBindings.Add("text", _
                    CategoriesBindingSource, "Description")

    'Initialize binding for Products data grid view
    If Not GridInitializedBoolean Then

        'Bind and format the grid
        ProductsDataGridView.DataSource = _
            ProductsBindingSource
        SetUpGridColumns()
        GridInitializedBoolean = True

    End If

    'Filter the products by category ID
    ProductsBindingSource.Filter = "CategoryID = '" & _
        CategoryIDTextBox.Text & "'"

End Sub

'===============================================================
'Create a sub routine to set up the grid columns and set the
'column widths.

Private Sub SetUpGridColumns()

    Try

        With Me.ProductsDataGridView
            'Set up column headers
            .Columns!category_id.HeaderText = "CategoryID"
            .Columns!product_id.HeaderText = "ProductID"
            .Columns!prodName.HeaderText = "Name"
            .Columns!supplier_id.HeaderText = "SupplierID"
            .Columns!quantity.HeaderText = "Quantity/Unit"
            .Columns!unit_price.HeaderText = "Unit Price"
            .Columns!in_stock.HeaderText = "Units In Stock"
            .Columns!on_order.HeaderText = "Units Ordered"
            .Columns!reorder.HeaderText = "Reorder Level"
            .Columns!discontinued.HeaderText = "Discontinued"

            'Set up column widths
            .Columns!category_id.Width = 100
            .Columns!product_id.Width = 75
            .Columns!prodName.Width = 30
            .Columns!lsupplier_id.Width = 75
            .Columns!quantity.Width = 35
            .Columns!unit_price.Width = 50
            .Columns!in_stock.Width = 75
            .Columns!reorder.Width = 90
        End With

    Catch ex As Exception

    End Try
End Sub

End Class

Answer 1

发现错误！这是一个简单的错误。

我有：

With ProductsBindingSource
     .DataSource = CategoriesBindingSource
     .DataMember = "ProductsToCategories"
End With

应该是:(使用绑定源而不是数据集）：/

 With ProductsBindingSource
            .DataSource = CategoriesProductsDataSet
            .DataMember = "products"
            .Sort = "ProductID"

手动数据库连接和控制填充错误

1 个答案: