表没有主键 idpdf

Question

为什么会出现这个错误

表没有主键。

虽然我在创建表 (pdfinfo) 期间将 (idpdf) 设为主要

在这一行

Dim row As DataRow = dt.Rows.Find(ComboBox1.SelectedValue)

 Private Sub mylib_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load


    adapter = New SqlDataAdapter("select * from pdfinfo ", connection)
    adapter.Fill(dt)

    ComboBox1.DataSource = dt
    ComboBox1.DisplayMember = "pdfname"
    ComboBox1.ValueMember = "idpdf"

    dt.Constraints.Add("Primary", dt.Columns("idpdf"), True)


End Sub

Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged

    Dim filename As String = ComboBox1.Text
    Dim row As DataRow = dt.Rows.Find(ComboBox1.SelectedValue)
    Dim file_data() As Byte = CType(row(2), Byte())
    Dim fs As New FileStream(filename, FileMode.OpenOrCreate, FileAccess.Write)

    fs.Write(file_data, 0, file_data.Length)
    fs.Close()

    Process.Start(filename)

End Sub

Answer 1

要定义表的主键，您应该使用PrimaryKey 属性，而不是用于外键或唯一约束的Constraints。

dt.PrimaryKey = New DataColumn() {dt.Columns("idpdf"))