从 VB.net 连接到 SQL 数据库时，“行/列不存在数据”

Posted 2023-05-07

【中文标题】从 VB.net 连接到 SQL 数据库时，“行/列不存在数据”

【英文标题】："No data exists for the row/column" when connecting to SQL database from VB.net

【发布时间】：2013-11-20 13:15:45

【问题描述】：

我正在尝试创建一个具有 datagridview 的程序，当用户单击视图中的单元格时，它会查看 SQL 数据库，从同一记录中的其他字段获取信息，并自动填充相应的文本表单中的框（通过操作字段名称完成）。

但是，由于某种原因，我收到一条错误消息： “InvalidOperationException 未处理” “行/列不存在数据”

这里是与这部分程序相关的代码：

Private Sub DataGridView1_CellMouseClick(sender As Object, e As DataGridViewCellMouseEventArgs) Handles dgvResults.CellMouseClick
    ' Set values in the text boxes to both corresponding to the film.
    Dim strFields() As String = "ID", "fName", "fGenre", "fSynopsis", "fAgeRating", "fActorsActresses", "fWebRating", "fNoReservations", "fWeeksRunning"

    Dim Con = New OleDbConnection("Provider=Microsoft.ACE.OLEDB.12.0;Data Source=ApplicationData.accdb;Persist Security Info=False;")
    Con.Open() 'Open the connection
    Dim Cmd As New OleDbCommand(StringBuilderCommand("*", "Films", dgvResults.CurrentCell.Value, "fName"), Con) 'Create a string by calling the StringBuilderCommand to combine the parameters together with quotes.

    Cmd.CommandType = CommandType.Text
    Dim Rdr As OleDbDataReader = Cmd.ExecuteReader()

    Dim intCount As Integer = 4 ' Create a loop variable.
    Do While Rdr.Read() Or intCount < 6 ' While this statement is 'TRUE', e.g. there is a valid record.

        strResult = "txt" & strFields(intCount).Replace("f", "") 'Remove any instances of 'f', e.g. the prefix of the string.

        txtActorsActresses.Text = StringBuilderCommand("*", "Films", dgvResults.CurrentCell.Value, "fName")
        Me.Controls(strResult).Text = Rdr.Item(strFields(intCount)) ' Suspect the error lies here.

        'Set the text-box to the correct value from the database.
        'This will allow me to go through several text boxes, and grab their corresponding values from the database.

        intCount = intCount + 1

        'Current error is because it cannot find any data beyond the first field taken.
        'I have no idea why this is. But if I change the starting intCount value, it will successfully take a different value.
    Loop

    Rdr.Close() 'Cleaning up.
    Cmd.Dispose()
    Con.Close()

    WebBrowser1.Navigate(dgvResults.CurrentCell.Value.Replace(" ", ".") & ".movie.poster.new.jpg.to") 'Grab the movie poster off the internet corresponding to the films name.
End Sub

Private Function StringBuilderCommand(Field, Table, CurrentCellValue, SearchParameter)
    'Creates a suitable SQL string.
    Dim MyStringBuilder As New StringBuilder("SELECT ")
    MyStringBuilder.Append("*") ' Append the parameter 'Field'.
    MyStringBuilder.Append(" FROM ") ' Append the SQL command 'FROM'.
    MyStringBuilder.Append(Table) ' Append the parameter 'Table'.
    MyStringBuilder.Append(" WHERE ") ' Append the SQL command 'WHERE'.
    MyStringBuilder.Append(SearchParameter) ' Append the parameter 'SearchParameter'.
    MyStringBuilder.Append("=""")
    MyStringBuilder.Append(CurrentCellValue) ' Append the parameter 'CurrentCellValue', representing the cell selected.
    MyStringBuilder.Append("""") 'Append a quotation mark.

    Return MyStringBuilder.ToString() ' Return it to the main program.

End Function

正在连接的数据库表：

在 Visual Studio 2012 Express 中的错误视图：

“dgvResults.CurrentCell.Value”的值是从数据库中提取的电影的名称（例如“为奴十二年”）。

我做错了什么？

谢谢， C.

【问题讨论】：

该错误非常具有描述性：确保您尝试访问的列/行完全存在于您的数据库中。

我认为在 Do While Rdr.Read() 或 intCount

Kostas 说得好……为什么要继续阅读超出阅读范围的内容？

@kostasch。不错的收获！

【参考方案1】：

问题是由您传递给阅读器的 strFields(intCount) 的值引起的。它不是有效的列索引。

【参考方案2】：

您可能希望先在字段上循环，然后再在 DataReader() 上循环，例如：

Do While Rdr.Read()

    For intCount as Integer = 4 to 6
      strResult = "txt" & strFields(intCount).Replace("f", "")
      txtActorsActresses.Text = StringBuilderCommand("*", "Films", dgvResults.CurrentCell.Value, "fName")
      Me.Controls(strResult).Text = Rdr.Item(strFields(intCount))
    Next

Loop

我删除了Dim intCount As Integer = 4，因为for next 循环不再需要它。