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I'm very new to programming and trying to write a program where it reads data about real estate properties from a txt file and has the option of adding another property on a new line under the rest of the properties in the txt file.

This is the sub handling the ReDim of the array at the moment:

Private Sub ExitSetTexts()

    Dim propertyId As String = arrListings(UBound(arrListings)).propertyId

    ReDim Preserve arrListings(UBound(arrListings) + 1)
    arrListings(UBound(arrListings)).address = txtAddress.Text
    arrListings(UBound(arrListings)).city = txtCity.Text
    arrListings(UBound(arrListings)).state = txtState.Text
    arrListings(UBound(arrListings)).postcode = txtPostcode.Text

    If rbHouse.Checked = True Then
        arrListings(UBound(arrListings)).type = "H"
    ElseIf rbUnit.Checked = True Then
        arrListings(UBound(arrListings)).type = "U"
    ElseIf rbAcreage.Checked = True Then
        arrListings(UBound(arrListings)).type = "A"

    End If

    arrListings(UBound(arrListings)).bedrooms = txtBedrooms.Text
    arrListings(UBound(arrListings)).salePrice = txtSalePrice.Text


    propertyId = CInt(propertyId.Trim.Remove(0, 1))
    propertyId = CInt(propertyId) + 1
    propertyId = CInt(propertyId).ToString("D4")
    propertyId = "  P" + propertyId
    arrListings(UBound(arrListings)).propertyId = propertyId


End Sub

When I run the program, enter all the details and then click on the button that runs this code, it throws a NullReferenceException saying "Additional information: Object reference not set to an instance of an object" and highlights this line:

arrListings(UBound(arrListings)).address = txtAddress.Text

I presume the ReDim is not working as intended because if I change it to (UBound(arrListings) - 1) then it will rewrite the new information ontop of the last line perfectly fine, but I cannot get it to write it on a new line.

Any guidance would be greatly appreciated,

Thanks.

Edit:

Forgot to add the part where I declare the array. I feel the way I've done this is rather dodgy but it was the first way I thought of and it seems to work.

In modMain is this;

Private listings() As Listing

Further in the Module is this function;

Public Function getListings() As Listing()

    Return listings
End Function

At the top of frmListings I've declared a second array;

Private arrListings() As Listing

frmListings then calls this function on frmListings_Load like this;

arrListings = getListings()

Then at the end when you close the form is calls a second sub which replaces the data in the original array with the altered data in the second array.

Like this;

setListings(arrListings)

Public Sub setListings(ByVal arrListings())
    listings = arrListings
End Sub

It's very messy but I couldn't work out how to use the array in the module from the form so I just did it like that.

Dale Maunder
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1 Answers1

2

When you resize the array, the new elements are Nothing by default so you need to set them to something before you use them:

ReDim Preserve arrListings(arrListings.Length)
arrListings(UBound(arrListings)) = New Listing
arrListings(UBound(arrListings)).address = txtAddress.Text
...

or 

Private Sub ExitSetTexts()

    Dim list = New Listing
    list.address = txtAddress.Text
    ...
    list.propertyId = propertyId

    ReDim Preserve arrListings(arrListings.Length)
    arrListings(UBound(arrListings)) = list

End Sub

A better answer would be to use Private arrListings As New List(Of Listing), but that would need a lot of changes in your code, so easier to leave it as array.

Slai
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