在vb.net中构建多维数组 [英] Building a multidimensional array in vb.net

问题描述

我正在尝试建立一个多维数组，该数组将为数据库中的每个记录保存两位信息，例如ID，说明.

这是我目前正在做的事情.

Dim mArray(,) As String
Dim i As Integer = 0
While cmdReader.Read()
    mArray(i,0) = cmdReader.Item("id")
    mArray(i,1) = cmdReader.Item("description")
    i = i + 1
End While

我在这里遇到的问题是，它不喜欢mArray(i,0)中的i.有人对此有任何想法吗?这是给出的错误Object reference not set to an instance of an object.

感谢所有帮助.

纳卢姆

解决方案

为什么不使用列表类和词典类

您可以创建一个字典列表，并使用键和值作为两个字符串.然后，键可以代表您的键(示例中的ID和说明，并且值可以是存储的值).

类似

Dim values As New List(Of Dictionary(Of String, String))()

然后在while循环中类似

values.Add(New Dictionary(Of String, String)() From { _
    {"id", cmdReader.Item("id")} _
})
values.Add(New Dictionary(Of String, String)() From { _
    {"description", cmdReader.Item("description")} _
})

然后您可以使用foreach

For Each value As Dictionary(Of String, String) In values
    Dim id As String = value("id")
    Dim description As String = value("description")
Next

或为

For i As Integer = 0 To values.Count - 1
    Dim value As Dictionary(Of String, String) = values(i)
    Dim id As String = value("id")
    Dim description As String = value("description")
Next

I'm trying to build up a multidimensional array which will hold two bits of info for each record in a database e.g. id, description.

This is what I am currently doing.

Dim mArray(,) As String
Dim i As Integer = 0
While cmdReader.Read()
    mArray(i,0) = cmdReader.Item("id")
    mArray(i,1) = cmdReader.Item("description")
    i = i + 1
End While

The problem I have here is that it doesn't like the i in mArray(i,0). Anyone have any ideas about this? This is the error that is given Object reference not set to an instance of an object.

Thanks for any and all help.

Nalum

解决方案

Why not rather make use of List Class and Dictionary Class

You can rather then create a List of Dictionaries, with the key and value both strings. The key can then represent your key (id and description in your example, and the value can be what ever was stored).

Something like

Dim values As New List(Of Dictionary(Of String, String))()

and then in the while loop something like

values.Add(New Dictionary(Of String, String)() From { _
    {"id", cmdReader.Item("id")} _
})
values.Add(New Dictionary(Of String, String)() From { _
    {"description", cmdReader.Item("description")} _
})

You could then use foreach

For Each value As Dictionary(Of String, String) In values
    Dim id As String = value("id")
    Dim description As String = value("description")
Next

Or a for

For i As Integer = 0 To values.Count - 1
    Dim value As Dictionary(Of String, String) = values(i)
    Dim id As String = value("id")
    Dim description As String = value("description")
Next

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