如何避免 IndexOutOfRangeException 索引 DataReader 列？

发布于 2024-08-20 22:32:04 字数 812 浏览 4 评论 0原文

我在“IndexOutOfRangeException”方面遇到了一些麻烦。我认为这是因为当代码尝试从数据库获取 DateModified col 时，它有时包含 NULL（用户自创建页面以来并不总是更新页面）。

这是我的代码；

s = ("select datemodified, maintainedby, email, hitcount from updates where id =   @footid")
Dim x As New SqlCommand(s, c)
x.Parameters.Add("@footid", SqlDbType.Int)
x.Parameters("@footid").Value = footid
c.Open()
Dim r As SqlDataReader = x.ExecuteReader
While r.Read
    If r.HasRows Then
        datemodified = (r("DateModified"))
        maintainedby = (r("maintainedby"))
        email = (r("email"))
        hitcount = (r("hitcount"))
    End If
End While
c.Close()

我认为（在读了一些msdn之后）添加了；

If r.HasRows Then 

End If

可以解决问题，但到目前为止添加后我仍然得到相同的旧 IndexOutOfRangeException

（ps，我已尝试将 datemodified 作为字符串/日期时间）

原文

I am having a little trouble with an 'IndexOutOfRangeException'. I think it is because when the code tries to get the DateModified col from the database it sometimes contains NULLS (the users haven't always updated the page since they created it).

Here is my code;

s = ("select datemodified, maintainedby, email, hitcount from updates where id =   @footid")
Dim x As New SqlCommand(s, c)
x.Parameters.Add("@footid", SqlDbType.Int)
x.Parameters("@footid").Value = footid
c.Open()
Dim r As SqlDataReader = x.ExecuteReader
While r.Read
    If r.HasRows Then
        datemodified = (r("DateModified"))
        maintainedby = (r("maintainedby"))
        email = (r("email"))
        hitcount = (r("hitcount"))
    End If
End While
c.Close()

I thought (after a bit of msdn) that adding;