mysql select语句未填充数据表

Question

我有一个 MySQL 对象，我试图从中选择所有数据并将其插入到数据表中，但是每次它到达有关所述数据表的第一个 if 语句时，它都会出现可能的空值错误

dbfile dbserver dbuser 和 dbpassw 都是在模块上设置的公共(public)变量。

可变尺寸

Dim cnn As New MySqlConnection()
Dim cmd As New MySqlCommand
Dim adptr As New MySqlDataAdapter
Dim filltab As DataTable

代码

        Dim cb As New MySqlConnectionStringBuilder
    cb.Database = dbfile
    cb.Server = dbserver
    cb.UserID = dbuser
    cb.Password = dbpassw
    Using cnn As New MySqlConnection(cb.ConnectionString)
        Using cmd As New MySqlCommand("SELECT * from gpstracking", cnn)
            Try
                cnn.Open()
                adptr = New MySqlDataAdapter(cmd)
                adptr.Fill(filltab)
            Catch ex As Exception
                MsgBox(ex.ToString)
            End Try
            If filltab.Rows.Count > 0 Then 'this is the row that the error for filltab being a null value hits
                pop = 0

                For pop As Integer = 0 To filltab.Rows.Count - 1
           '         WebBrowser1.Document.InvokeScript("AddMarker", New Object() {"Unit: " & filltab.Rows(pop)("unitnumb") & " at " & filltab.Rows(pop)("time"), filltab.Rows(pop)("lat"), table.Rows(pop)("long")})
                Next
            End If
        End Using
    End Using

有一个错误

adptr.Fill(filltab)  'Exception:Thrown: "Value cannot be null." (System.ArgumentNullException)

我还刚刚注意到它在

上宣布“无法收集详细信息”

            Catch ex As Exception
                MsgBox(ex.ToString)
            End Try

Answer 1

我不知道vb语法，但你有Dim filltab As DataTable，没有New(就像在其他维度中一样)，我猜MySqlDataAdapter.Fill 要求参数不为空。只是猜测。