vb.net 中的数据读取器

发布于 2024-09-10 07:21:47 字数 443 浏览 6 评论 0原文

请帮助，我如何制作一个与此 for 循环等效的 while 循环。这样我就可以读取 mysql 数据库表中的一行并将其显示在 vb.net 的组合框中。

我使用此代码，但如果行中添加了 3 个或更多项目，它绝对没有用：

Dim i As Integer
        Dim rdr As Odbc.OdbcDataReader
        rdr = con.readfrom_drug_type_table()
    For i = 0 To 1
        If rdr.HasRows = True Then
            rdr.Read()

            ComboBox2.Items.Add(rdr("Drug_type"))
        End If
    Next i

我想读取 Drug_type 行中的所有数据请帮忙，谢谢

原文

Please help, how do I make a while loop equivalent of this for loop. So that I could read from one row in the table of mysql database and display it on the combobox in vb.net.

I use this code, but its definitely not useful if there are 3 or more items that are added in the row:

Dim i As Integer
        Dim rdr As Odbc.OdbcDataReader
        rdr = con.readfrom_drug_type_table()
    For i = 0 To 1
        If rdr.HasRows = True Then
            rdr.Read()

            ComboBox2.Items.Add(rdr("Drug_type"))
        End If
    Next i

I want to read all the data from that the Drug_type row
Please help, thanks

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回忆凄美了谁 2024-09-17 07:21:47

如果您只想读取第一行而不是只使用

If rdr.Read() Then 
     ComboBox2.Items.Add(rdr("Drug_type")) 
End If

Update

Try
    myConnection = New SqlConnection("server=localhost;uid=sa;pwd=;database=pubs")
    'you need to provide password for sql server
    myConnection.Open()
    myCommand = New SqlCommand("Select * from discounts", myConnection)
    dr = myCommand.ExecuteReader

        While dr.Read()
            WriteLine(dr(0))
            WriteLine(dr(1))
            WriteLine(dr(2))
            WriteLine(dr(3))
            WriteLine(dr(4))
            ' writing to console
        End While
Catch
End Try
dr.Close()
myConnection.Close()

If you want to read only first row than just use

If rdr.Read() Then 
     ComboBox2.Items.Add(rdr("Drug_type")) 
End If

Update

Try
    myConnection = New SqlConnection("server=localhost;uid=sa;pwd=;database=pubs")
    'you need to provide password for sql server
    myConnection.Open()
    myCommand = New SqlCommand("Select * from discounts", myConnection)
    dr = myCommand.ExecuteReader

        While dr.Read()
            WriteLine(dr(0))
            WriteLine(dr(1))
            WriteLine(dr(2))
            WriteLine(dr(3))
            WriteLine(dr(4))
            ' writing to console
        End While
Catch
End Try
dr.Close()
myConnection.Close()

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扭转时空 2024-09-17 07:21:47

@普拉奈
您不需要嵌套循环。

Try
    myConnection = New SqlConnection("server=localhost;uid=sa;pwd=;database=pubs")
    myConnection.Open()
    myCommand = New SqlCommand("Select * from discounts", myConnection)
    dr = myCommand.ExecuteReader()
    While dr.Read()
        WriteLine(dr(0))
        WriteLine(dr(1))
        WriteLine(dr(2))
        WriteLine(dr(3))
        WriteLine(dr(4))
    End While
    dr.Close()
Finally
    myConnection.Close()
End Try

@pranay
You don't need the nested loops.

Try
    myConnection = New SqlConnection("server=localhost;uid=sa;pwd=;database=pubs")
    myConnection.Open()
    myCommand = New SqlCommand("Select * from discounts", myConnection)
    dr = myCommand.ExecuteReader()
    While dr.Read()
        WriteLine(dr(0))
        WriteLine(dr(1))
        WriteLine(dr(2))
        WriteLine(dr(3))
        WriteLine(dr(4))
    End While
    dr.Close()
Finally
    myConnection.Close()
End Try

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