视觉基本阵列搜寻

Question

I'm trying to search an array for previous entries from a user inputted text box that match new incoming entries. Is there any way to do this in Visual Basic? I'm converting my code from C# and Visual Basic keeps giving me an error "Object reference not set to an instance of an object." With this statement, the code skips the if block to check for matching text because arrayName(i) or 0 in this case is currently NOTHING. If i take out this if block and it reaches the name check, then it causes an error because there is nothing in arrayName(i) to convert to upper string.

So here's my code..My question again was is there an easier way to search previous entries from an array to newly input entries.

Edit: details

This is the array declaration Dim arrayName() = New String(2) {} and when it gets to If arrayName(i).ToString.ToUpper = txtInput.Text.ToUpper Then it says "Object variable or With block variable not set." "NullReferenceException was unhandled by user code". The "x" in the code is the fixed length of the array, which is 2 in this case.

Dim i As Integer = 0
            While x >= i
                If arrayName(i) IsNot Nothing Then
                    If arrayName(i).ToString.ToUpper = txtInput.Text.ToUpper Then
                        match = False
                        lblName.Text = "Enter a unique name"
                    End If
                End If
                    i += 1
            End While

Answer 1

Since you don't want to use built-in search functions...Try this...

Declare this under Global Scope...So put it just under the form class...

Dim counter As Integer = 0
Dim arrayname(10) As String

Add a button control... and add this code...

 Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
    If counter < 10 Then
        Dim input As String = InputBox("Please input name.")
        If input = "" Then
            MsgBox("Nothing entered!")
            Exit Sub
        End If
        For x = 0 To 10
            If UCase(input) = UCase(arrayname(x)) Then
                MsgBox("Duplicate name!")
                Exit Sub
            End If
        Next x
        arrayname(counter) = input
        counter += 1
    Else
        MsgBox("Array full!")
    End If
End Sub

That's it. Edit to suit your exact needs. Tell me if it works :)

Answer 2

Your code snippet hasn't defined x .

You can search your array efficiently with a little bit of LINQ:

Dim listFound As IEnumarable(String) = From item In arrayName _
                                       Where item.ToString.ToUpper _
                                       = txtInput.Text.ToUpper _
                                       Select item
If listFound.Count > 0 Then
    lblName.Text = "Enter a unique name"
End If

Or you can manually search the array, but I think this is more efficient that the method you are using:

Dim Match As Boolean = False

For i As Integer = 0 To arrayName.Count - 1
    If Not IsNothing(arrayName(i)) Then
        If arrayName(i).ToString.ToUpper = txtInput.Text.ToUpper Then
            Match = True
            Exit For
        End If
    End If
Next
If Match Then
    lblName.Text = "Enter a unique name"
End If

Two last items of note: arrayName(i).ToString.ToUpper is equivalent to UCase(arrayName(i)) . You may want to perform some speed tests to see which is actually faster.

Also, Dim myArray As String(3) is not the same thing in VB as Dim myArray() = New String(3) {} . The first example results in a 1 dimensional array. The last example results in a 2 dimensional array.