Check if a list of strings contains a value

Question

I have:

Public lsAuthors As List(Of String)

I want to add values to this list, but before adding I need to check if the exact value is alre

Answer 1

To check whether an element is present in a list you can use the list.Contains() method. If you are using a button click to populate the list of strings then see the code:

Public lsAuthors As List(Of String) = New List(Of String) ' Declaration of an empty list of strings

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click ' A button click populates the list
    If Not lsAuthors.Contains(TextBox2.Text) Then ' Check whether the list contains the item that to be inserted
        lsAuthors.Add(TextBox2.Text) ' If not then add the item to the list
    Else
        MsgBox("The item Already exist in the list") ' Else alert the user that item already exist
    End If
End Sub

Note: Line by line explanation is given as comments