VB stringbuilder Contains

Question

I have a stringbuilder in VB

I like to check to see if it contains a value if so I like to do something:

If strMsg.Contains("<table>") Then
  ' strMsg = strMsg + "<br/><br/><br/>"
  strMsg.Append("<br/><br/><br/>")
End If

I tried the above but said contains is not a member of System.Text.StringBuilder.

What can I use in place of Contains

Answer 1

I would check your inputs into the StringBuilder for this condition.

Dim hasTable As Boolean = False

' Check inputs, set hasTable to True if needed

If hasTable Then
    strMsg.Append("<br/><br/><br/>")
End If

Answer 2

Contains() is not among Stringbuilder's methods. That said, you have a couple options...

1.: Test your values on the way in and maintain a boolean flag for your append <br> tags state.

2.: Perform ToString() and call Contains() from the result:

if strMsg.ToString().Contains("<table>") then '...

3.: Implement IndexOf() and/or Contains() yourself:

Module StringBuilderExtensions

    <Extension()>
    Public Function IndexOf(ByVal sb As StringBuilder, ByVal value As String) As Integer

        For i As Integer = 0 To sb.Length - value.Length - 1

            For y As Integer = 0 To value.Length - 1

                If value(y) <> sb(i + y) Then

                    Exit For

                ElseIf y = value.Length - 1 Then

                    Return i

                End If

            Next

        Next

        Return -1

    End Function

    <Extension()>
    Public Function Contains(ByVal sb As StringBuilder, ByVal value As String) As Boolean

        Return sb.IndexOf(value) > -1

    End Function

End Module

Disclaimer: This hasn't been tested for performance... and Michael Haren's comment was directed at the ToString() option.