VB visual studio中执行阅读器的问题 [英] problem with execute reader in VB visual studio

问题描述

嗨

当我运行以下代码时，在声明数据读取器博士时出现错误

when I run the following code I get an error where I declare dr the data reader

在行'dr = cmd.ExecuteReader()'上出现以下错误:

on line 'dr = cmd.ExecuteReader()' I am getting the following error:

System.Data.OleDb.OleDbException:'未为一个或多个必需参数提供值.'

System.Data.OleDb.OleDbException: 'No value given for one or more required parameters.'

只是想知道是否有人知道如何解决这个问题?

just wondering if anyone knows how to solve this?

Private Sub carFinder(b As String, m As String, s As String, d As String, e As String)
        myConnection.ConnectionString = My.Forms.Main.connString
        myConnection.Open()
        Dim match As String
        match = "SELECT * FROM CxDetails WHERE (CBrand = '" & b & "' and CModel = '" & m & "' 
                and CSpec ='" & s & "'and CNoOfDoors = '" & d & "' and CEngineSize ='" & e & "')"
        Dim cmd As OleDbCommand = New OleDbCommand(match, myConnection)
        dr = cmd.ExecuteReader()
        myConnection.Close()


        Dim CO2e As String = dr("CCO2")
        Dim COTR As String = dr("COTR")

推荐答案

我看不到问题，但是从今天的VB开始使用了更多内容，我在该样式，当然未经测试，我没有您的数据库.

I don't see the problem, but use a little bit more from todays VB, I changed your code in that style, of course not tested, I don't have your database. 

    Private Sub carFinder(b As String, m As String, s As String, d As String, e As String)
        Dim CO2e As String
        Using myConnection.ConnectionString = My.Forms.Main.connString
            myConnection.Open()
            Dim match As String
            match = "SELECT  * FROM CxDetails WHERE (CBrand = @b and CModel = @m  
                and CSpec = @s and CNoOfDoors = @d and CEngineSize = @e)"
            Using cmd As New OleDb.OleDbCommand(match, myConnection)
                cmd.Parameters.AddWithValue("@b", b)
                cmd.Parameters.AddWithValue("@m", m)
                cmd.Parameters.AddWithValue("@s", s)
                cmd.Parameters.AddWithValue("@d", d)
                cmd.Parameters.AddWithValue("@e", e)
                Dim dr = cmd.ExecuteReader()
                While dr.Read
                    CO2e = dr("CC2E") 'be aware this is case sensitive
                    'The rest
                End While
            End Using
        End Using
    End Sub

因此，请注意上面的代码中的typeos和小错误.

Therefore watch typeos and small mistakes in the code above. 

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