text file compare not working with split string

[bOywOnder123]

hi guys could someone explain to me why this does not work.

I basically have to text files called Books and NewBooks...

The text files are populated from a web request and the info is then parsed into the text files...when I start the program Books and new books are identical and pretty much a copy of each other.

more web requests are done to update the NewBooks text file and when I compare them if there is a line in NewBooks that is not in Books it adds that line to a third text file called myNewBooks. Now my initial code that I will show here works as I expected

Dim InitialBooks = File.ReadAllLines("Books.json")
    Dim TW As System.IO.TextWriter
    'Create a Text file and load it into the TextWriter 
    TW = System.IO.File.CreateText("myNewBooks.JSON")

    Dim NewBooks = String.Empty
    Using reader = New StreamReader("NewBooks.json")
        Do Until reader.EndOfStream
            Dim current = reader.ReadLine
            If Not InitialBooks.Contains(current) Then 
                NewBooks = current & Environment.NewLine

                TW.WriteLine(NewBooks)
                TW.Flush()
                'Close the File 
            End If
        Loop
    End Using
    TW.Close() : TW.Dispose()

but because part of the string in my text file lines contain a url which sometimes I find the same book with a different url... I was getting duplicate entries of books becuase the url was the only difference. So I thought that I would split the string before the url so that I just compare the title and description and region ...fyi a line in my text files look similar to this:

{ "Title": "My Title Here", "Description": "My Description Here", "Region": "My Region Here", "Url": "My Url Here", "Image": "My Image Here" };

So a fellow today helped me figure out how to split my line so it looks more like this:

{ "Title": "My Title Here", "Description": "My Description Here", "Region": "My Region Here", "Url"

which is great but now when I compare it does not see that the first line contains the split line and I don't understand why... here is the code after it was modified.

Dim InitialBooks = File.ReadAllLines("Books.json")
    Dim TW As System.IO.TextWriter
    'Create a Text file and load it into the TextWriter 
    TW = System.IO.File.CreateText("myNewBooks.JSON")

    Dim NewBooks = String.Empty
    Using reader = New StreamReader("NewBooks.json")
        Do Until reader.EndOfStream
            Dim current = reader.ReadLine
            Dim splitAt As String = """Url"""
            Dim index As Integer = current.IndexOf(splitAt)
            Dim output As String = current.Substring(0, index + splitAt.Length)
            If Not InitialBooks.Contains(output) Then 
                NewBooks = current & Environment.NewLine

                TW.WriteLine(NewBooks)
                TW.Flush()
                'Close the File 
            End If
        Loop
    End Using
    TW.Close() : TW.Dispose()

Your wisdom would be appreciated!!

[si_the_geek]

The .Contains method of an Array or List loops the items to see if there is one that is an exact match, and returns true if there is.

That failed when the URLs were different, and it also fails when you pass in part of the text (because it cannot be equal to a full item).

Due to the URL issue you do want to check for part of the text, but you can't use the .Contains method of the array for that, instead the easy to understand way would be to write your own loop to check the items (using the .StartsWith method of the item). Use a boolean variable which you set before the loop (to indicate 'not found'), and if you find a matching item change the value of the boolean (to indicate 'found'). You can then change your If statement to check the boolean variable.

[PlausiblyDamp]

Just an idea, have you considered defining a class for a book and deserializing the json into instances of this class? That way you could directly compare properties rather than relying on string comparisons.

[bOywOnder123]

The .Contains method of an Array or List loops the items to see if there is one that is an exact match, and returns true if there is.

That failed when the URLs were different, and it also fails when you pass in part of the text (because it cannot be equal to a full item).

Due to the URL issue you do want to check for part of the text, but you can't use the .Contains method of the array for that, instead the easy to understand way would be to write your own loop to check the items (using the .StartsWith method of the item). Use a boolean variable which you set before the loop (to indicate 'not found'), and if you find a matching item change the value of the boolean (to indicate 'found'). You can then change your If statement to check the boolean variable.

Thank you will look into this it doesn't seem like I can use the startswith method directly on the string I created from reading all the line of the txt file but maybe I can split it into an array somehow...thanks for the insight.

[si_the_geek]

You don't need to split InitialBooks into an array, because it already is one.

The return value of File.ReadAllLines is: "A string array containing all lines of the file."
https://msdn.microsoft.com/en-us/lib...v=vs.110).aspx

[bOywOnder123]

hey there again ty for your help earlier in this post...I did manage to get that part worked out...but now following the same logic I keep getting an Exception error that string cannot be converted to integer and not quite sure why...Ive tried adding the toString() method to many different places to try and resolve and nothing has worked...can you please just glance over this and see where I am being dumb. The files are still in the same format as stated in my Initial question...and basically trying to see when a new item is found to see if it starts with all the lines in History split it at the word """URL"""

I commented just above the if statement that throws the exception.

the exact error is:

System.InvalidCastException: 'Conversion from string "{ "Title": "Item 1" to type 'Integer' is not valid.'

Inner Exception
FormatException: Input string was not in a correct format.

Dim History = File.ReadAllLines("history.json")
Dim NewestItems = File.ReadAllLines("items.json")
Dim InitialItems = File.ReadAllLines("Init-items.json")

For x As Integer = 0 To InitialItems.Length - 1
            Dim current As String = InitialItems(0)
            Dim splitAt As String = """Url"""
            Dim index As Integer = current.IndexOf(splitAt)
            Dim output As String = current.Substring(0, index + splitAt.Length)
            Dim recurringItemFound = 0
            If Not NewestItems(x).StartsWith(output) And Not History.Contains(NewestItems(x)) Then

                If cbxRecurringItemsOff.Checked = True Then
                    For Each RecurringItem In History
                        Dim indexHistory As Integer = NewestItems(x).IndexOf(splitAt)
                        Dim outputHistory As String = NewestItemss(x).Substring(0, indexHistory + splitAt.Length)
                        '********the below if statement throws an Exception error*********
                        If NewestItems(RecurringItem).StartsWith(outputHistory) Then
                            recurringItemFound = 1
                        End If
                    Next
                End If
Next

[si_the_geek]

NewestItems is an array (the lines of the file "items.json"), and to refer to the elements of an array you put an integer (number without decimal places) in brackets after the array name, eg:

myVariable =  NewestItems(3)

...will store the fourth item in the array to a variable (it is the fourth item because counting starts at 0).

If you want to, you can use a variable instead of a fixed number, eg:

myInteger = 3
myVariable =  NewestItems(myInteger)

...which will return the same as before, because the variable contains the same number.

In this case you are using NewestItems(RecurringItem) , but is the variable RecurringItem numeric? No it isn't, it is one of the items from the History array (which is also made from the lines from a file, and therefore is a String - as the error message shows it doesn't contain just a number).

I am not sure, but I'm guessing that instead of NewestItems(RecurringItem) you intended to use just RecurringItem


There are some other things about your code that seem odd, such as:

For x As Integer = 0 To InitialItems.Length - 1
            Dim current As String = InitialItems(0)

...did you mean InitialItems(x) ?

                        Dim indexHistory As Integer = NewestItems(x).IndexOf(splitAt)
                        Dim outputHistory As String = NewestItemss(x).Substring(0, indexHistory + splitAt.Length)

...are those two different variables, or is one of them a typo? (if it is a typo, let Visual Studio automatically tell you about that by adding Option Explicit to the top of the code file)