CODEWITHSUNDEEP
vb.netmultidimensional-arraywhile-loop
Nalum
Nalum

Reputation: 4213

Building a multidimensional array in vb.net

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

Upvotes: 10

Views: 95660

Answers (5)

Stefan Köhli
Stefan Köhli

Reputation: 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

Upvotes: 0

FariD Partonia
FariD Partonia

Reputation: 1

Correct it by

Dim mArray(,) As String = ""

Upvotes: -2

Anthony
Anthony

Reputation: 61

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

Upvotes: 6

Adriaan Stander
Adriaan Stander

Reputation: 166586

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

Upvotes: 14

Drake
Drake

Reputation: 8392

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.

Upvotes: 3

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