Building a multidimensional array in vb.net

Question

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

Adriaan Stander · Accepted Answer · 2010-11-23 11:07:44Z

14

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

edited Nov 23, 2010 at 11:07

answered Nov 23, 2010 at 11:01

Adriaan Stander

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5 Comments

Nalum Over a year ago

Would I then be able to loop over that using for/foreach? Don't know much about .net was thrown into it for this project.

Nalum Over a year ago

Thanks astander, will give this a shot, looks like it will do the trick.

Nalum Over a year ago

Took a bit of fiddling but I got it working, Thanks astander.

bgmCoder Over a year ago

Any idea how to sort this? stackoverflow.com/questions/15819207/…

Cary Bondoc Over a year ago

For me it says The given key was not present in the dictionary..

Anthony · Accepted Answer · 2012-12-18 10:34:10Z

6

Try this

Dim mArray(1,1) 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
    ReDim Preserve mArray(i,1)
End While

answered Dec 18, 2012 at 10:34

Anthony

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Comments

Community · Accepted Answer · 2017-05-23 12:08:28Z

3

The problem is that you are not initializing the array.

This should work, until i will not reach the limits set in the initialization.

Dim mArray(100,100) 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

But if the array limits are not known I suggest to follow astander's suggestion.

edited May 23, 2017 at 12:08

CommunityBot

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answered Nov 23, 2010 at 11:07

Drake

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1 Comment

Nalum Over a year ago

Unfortunately the limits are unknown, I tired doing Dim mArray(,2) but was told to put a number in for the first part of the array.

barbsan · Accepted Answer · 2018-11-21 11:14:43Z

1

This works for me:

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

values.Add(New Dictionary(Of String, String)() From {{"quarter", q1.ToString}, {"year", y1.ToString}})
values.Add(New Dictionary(Of String, String)() From {{"quarter", q2.ToString}, {"year", y2.ToString}})
values.Add(New Dictionary(Of String, String)() From {{"quarter", q3.ToString}, {"year", y3.ToString}})
values.Add(New Dictionary(Of String, String)() From {{"quarter", q4.ToString}, {"year", y4.ToString}})

For Each value As Dictionary(Of String, String) In values
    Dim quarter As String = value("quarter")
    Dim year As String = value("year")
    Debug.Print(quarter & "/" & year)
Next

edited Nov 21, 2018 at 11:14

barbsan

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answered Nov 21, 2018 at 10:50

Stefan Köhli

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Comments

Paul Roub · Accepted Answer · 2017-06-26 21:31:22Z

-2

Correct it by

Dim mArray(,) As String = ""

edited Jun 26, 2017 at 21:31

Paul Roub

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answered Jun 23, 2017 at 9:21

FariD Partonia

1

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