Question

我的论文有问题。它不断显示消息＆＃34;位置0没有行。＆＃34;。即使我的MySql数据库中有数据。请帮忙，我是新手。谢谢！

Private Sub frmAccountEdit_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        txtUserID.Text = frmAccountList.AccountCaller
        da = New MySqlDataAdapter("SELECT * FROM tbl_account WHERE userid = '" & txtUserID.Text & "'", con)
        ds.Reset()
        da.Fill(ds)

        Try
                cmbAccType.SelectedIndex = ds.Tables(0).Rows(0)(1).ToString
                txtUsername.Text = ds.Tables(0).Rows(0)(2).ToString
                txtPassword.Text = ds.Tables(0).Rows(0)(3).ToString
                txtFirst.Text = ds.Tables(0).Rows(0)(4).ToString
                txtLast.Text = ds.Tables(0).Rows(0)(5).ToString
        Catch ex As Exception
            MessageBox.Show(ex.Message, "ERROR!", MessageBoxButtons.OK, MessageBoxIcon.Error)
        End Try
End Sub

Answer 1

运行mysql workbench并在那里尝试查询以使其工作。您将从查询中获得更多信息。如果没有第0行，则查询不返回任何内容。在尝试访问位置0之前查找行计数。

我参加了一个我一直用的课。您也不希望使用类似的文本框对查询进行硬编码。您可能会受到SQL注入的攻击。使用像这样的东西

sqlquery = "SELECT * FROM tbl_account WHERE userid=@coluid"

然后使用我班级的addparam函数添加文本框

dim xDB as new mysql
xdb.addparam("@coluid", txtuserid.text)
xdb.execquery(sqlquery)
if xdb.rows.count>0 then 'you have a record

Imports MySql.Data.MySqlClient

Public Class mysql

    'Connection string for mysql
    Public SQLSource As String = "Server=1.1.1.1;userid=xuser;password=xpassword;"

    'database connection classes

    Private DBcon As New MySqlConnection
    Private SQLcmd As MySqlCommand
    Public DBDA As New MySqlDataAdapter
    Public DBDT As New DataTable
    ' parameters
    Public Params As New List(Of MySqlParameter)

    ' some stats
    Public RecordCount As Integer
    Public Exception As String
    Sub ExecQuery(SQLQuery As String)

        DBcon.ConnectionString = SQLSource
        Try
            DBcon.Open()
            SQLcmd = New MySqlCommand(SQLQuery, DBcon)
            'loads params into the query
            Params.ForEach(Sub(p) SQLcmd.Parameters.AddWithValue(p.ParameterName, p.Value))

            'or like this is also good
            'For Each p As MySqlParameter In Params
            ' SQLcmd.Parameters.AddWithValue(p.ParameterName, p.Value)
            ' Next
            ' clears params

            Params.Clear()
            DBDA.SelectCommand = SQLcmd
            DBDA.Update(DBDT)
            DBDA.Fill(DBDT)
            DBcon.Close()
        Catch ex As MySqlException
            Exception = ex.Message
        Finally
            DBcon.Dispose()
        End Try
    End Sub
    ' add parameters to the list
    Public Sub AddParam(Name As String, Value As Object)
        Dim NewParam As New MySqlParameter(Name, Value)
        Params.Add(NewParam)
    End Sub
End Class

编辑表单加载。错误：＆＃34;位置0没有行。＆＃34; [VB.net]

1 个答案: