VB.NET System.Data.EvaluateException：'无法对 System.Int32 和 System.String 执行'='操作。'

Question

我有一个连接到我的项目的 Access 数据库，我在这里要做的是在连接到 datagridview 上的字段的组合框中显示一些值。

这是我得到的错误

System.Data.EvaluateException: 'Cannot perform '=' operation on System.Int32 and System.String.'

这里是代码

   Private Sub form_inventory_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        'TODO: This line of code loads data into the 'InventoryManager2DataSet.Sub_Category' table. You can move, or remove it, as needed.
        Me.Sub_CategoryTableAdapter.Fill(Me.InventoryManager2DataSet.Sub_Category)

        'TODO: This line of code loads data into the 'InventoryManager2DataSet.Sub_Category' table. You can move, or remove it, as needed.
        Me.Sub_CategoryTableAdapter.Fill(Me.InventoryManager2DataSet.Sub_Category)
        'TODO: This line of code loads data into the 'InventoryManager2DataSet.Inventory' table. You can move, or remove it, as needed.
        Me.InventoryTableAdapter.Fill(Me.InventoryManager2DataSet.Inventory)
        Me.DataGridViewTextBoxColumn8.DisplayMember = "Category"
        Me.DataGridViewTextBoxColumn8.ValueMember = "ID"
        Me.DataGridViewTextBoxColumn8.DataSource = Sub_CategoryBindingSource


        With Sub_CategoryComboBox
            .DataSource = Sub_CategoryBindingSource
            .DisplayMember = "Category"
            .ValueMember = "Id"
        End With

    End Sub

    Private Sub Sub_CategoryComboBox_SelectedIndexChanged(sender As Object, e As EventArgs) Handles Sub_CategoryComboBox.SelectedIndexChanged
        If Me.Sub_CategoryComboBox.SelectedIndex = -1 Then
            InventoryBindingSource.Filter = Nothing
        Else
            InventoryBindingSource.Filter = $"convert[Sub Category] = '{Me.Sub_CategoryComboBox.SelectedValue}'"
        End If
    End Sub

这部分代码触发了错误

 InventoryBindingSource.Filter = $"convert[Sub Category] = '{Me.Sub_CategoryComboBox.SelectedValue}'"

我可以让它在没有连接的情况下工作一个干净的组合框，但是当它连接到字段时我无法让它工作。

• Sub_Category 是一个表
• 子类别是长整数
• 类别是短文本

子类别是从包含类别字段的子类别表中查找的字段。

这里是可视化的：

Answer 1

您说组合框的值将是Id 属性

With Sub_CategoryComboBox
    .DataSource = Sub_CategoryBindingSource
    .DisplayMember = "Category"
    .ValueMember = "Id" ' This line!
End With

然后您尝试将组合框的值（Id）与文本字段进行比较。

我现在不知道你的业务逻辑应该是什么，但我怀疑这可能是你需要的：

With Sub_CategoryComboBox
    .DataSource = Sub_CategoryBindingSource
    .DisplayMember = "Category"
    .ValueMember = "Category" ' Changed!
End With