Array contains checking in vb.net

Hello,

Can it be done any better:

   Dim  Arr3 As New ArrayList
  Dim SQLdr As SqlDataReader
  Dim StrCol3 As String

    If StrCol3 <> String.Empty Then
                    If IsDBNull(SQLdr(StrCol3)) = False Then
                        StrColval3 = SQLdr(StrCol3)
                        StrColval3 = StrColval3.Trim
                        If StrColval3 <> String.Empty Then
                            'Check for duplicates in array
                            If Not (Arr3.Contains(StrColval3)) AndAlso Not (Arr3.Contains(StrColval3.ToLower)) Then
                                If Not (Arr3.Contains(StrColval3.ToUpper)) Then
                                    Arr3.Add(SQLdr(StrCol3))
                                End If
                            End If
                            End If
                    End If
                End If

Cheers
RIASAsked:
Who is Participating?
 
it_saigeConnect With a Mentor DeveloperCommented:
RIAS,

ArrayList has a Contains method which uses the Object.Equals method to compare the objects in the array with the object specified in the parameter.  My knock against using an ArrayList, though, stems from the fact that ArrayList Objects are not type specific.  Proof of concept -
Module Module1
	ReadOnly list As New ArrayList From
		{
			New Byte(),
			1,
			12.46F,
			2.38D,
			"Jeffrey",
			New Byte(10)() {}
		}

	Sub Main()
		If list.Contains(2.38F) Then
			Console.WriteLine("List has a {0} type with a value of {1}", 2.38F.GetType(), 2.38F)
		Else
			Console.WriteLine("List does not have a {0} type with a value of {1}", 2.38F.GetType(), 2.38F)
		End If

		If list.Contains(2.38D) Then
			Console.WriteLine("List has a {0} type with a value of {1}", 2.38D.GetType(), 2.38D)
		Else
			Console.WriteLine("List does not have a {0} type with a value of {1}", 2.38D.GetType(), 2.38D)
		End If
		Console.ReadLine()
	End Sub
End Module

Open in new window

Produces the following output -Capture.JPG
Instead, I would recommend you use one of the collections in System.Collections.Generic.  Most likely List<T> (for VB.NET that is List(Of T)) as alluded to by Andy previously.

Using a List(Of String) we could really improve your code; e.g. -
Function FillList(column As String) As List(Of String)
	Dim list As New List(Of String)
	Dim SQLdr As SqlDataReader
	Dim result As String

	If column <> String.Empty Then
		If Not IsDBNull(SQLdr(column)) Then
			result = SQLdr(column)
			result = result.Trim
			If Not String.IsNullOrEmpty(result) AndAlso Not list.Contains(result, StringComparer.OrdinalIgnoreCase) Then
				list.Add(result)
			End If
		End If
	End If
	Return list
End Function

Open in new window

Ofcourse if you are using .NET 4 or higher, then you can get rid of the Trim and use String.IsNullOrWhitespace instead; e.g. -
Function FillList(column As String) As List(Of String)
	Dim list As New List(Of String)
	Dim SQLdr As SqlDataReader
	Dim result As String

	If column <> String.Empty Then
		If Not IsDBNull(SQLdr(column)) Then
			result = SQLdr(column)
			If Not String.IsNullOrWhiteSpace(result) AndAlso Not list.Contains(result, StringComparer.OrdinalIgnoreCase) Then
				list.Add(result)
			End If
		End If
	End If
	Return list
End Function

Open in new window


Simple proof of concept -
Imports System.Data.SqlClient

Module Module1
	ReadOnly data As New List(Of String) From
		{
			"First",
			" ",
			"Second",
			"Third",
			"Fourth",
			" ",
			"sEcOnd"
		}

	Sub Main()
		Dim list As New List(Of String)
		For Each item In data
			If Not String.IsNullOrWhiteSpace(item) AndAlso Not list.Contains(item, StringComparer.OrdinalIgnoreCase) Then
				list.Add(item)
			End If
		Next

		For Each item In list
			Console.WriteLine(item)
		Next
		Console.ReadLine()
	End Sub
End Module

Open in new window

Which produces the following output -Capture.JPG
-saige-
0
 
AndyAinscowFreelance programmer / ConsultantCommented:
https://msdn.microsoft.com/en-us/library/yw84x8be(v=vs.110).aspx

You could use the Array.Exists method, supply your own comparison function that converts the array member and what is being checked for  to both upper (or lowercase) so that

                            If Not (Arr3.Contains(StrColval3)) AndAlso Not (Arr3.Contains(StrColval3.ToLower)) Then
                                If Not (Arr3.Contains(StrColval3.ToUpper)) Then
                                    Arr3.Add(SQLdr(StrCol3))
                                End If
                            End If

can be replaced by
                                If Not (Arr3.Exists(YourComparisonFunctionGoesHere(StrColval3.ToUpper))) Then
                                    Arr3.Add(SQLdr(StrCol3))
                                End If


ps.  Arrays are fairly outdated, consider using another type of container - depends on just what you want to do
0
 
RIASAuthor Commented:
Cheers! What is the alternative to array?
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RIASAuthor Commented:
YourComparisonFunctionGoesHere can you give a suggestion?
0
 
AndyAinscowFreelance programmer / ConsultantCommented:
Comparison:  There is an example in the link I supplied.

Alternative:  Depends on what you require.  A List<T> is often good but under certain requirements a dictionary or queue or stack.....
0
 
RIASAuthor Commented:
Ok mate will give a try and get back !
0
 
RIASAuthor Commented:
Andy ,
It says Exists is not a member of arraylist?
0
 
AndyAinscowFreelance programmer / ConsultantCommented:
Erm.  Exists should be a member of Array, but I see you talked of an array in the question title but used an arraylist instead in the question.
0
 
AndyAinscowConnect With a Mentor Freelance programmer / ConsultantCommented:
You could use a BinarySearch instead of Exists:
https://msdn.microsoft.com/en-us/library/b4y1ah87(v=vs.110).aspx
and use a case insensitive comparer.
0
 
RIASAuthor Commented:
Thanks Andy!
Thank you Saige Sir!
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