How can i go back previous observed string

Question

Example

String context = string.Emty;

private void BtnForward_Click(object sender, RoutedEventArgs e)
{
  //First Click
  context = Abcd;
  TextboxText.Text = context; //Abcd 
  //Second Click
  TextboxText.Text = context; //new context = SADASD
  //Third Forth Fift click new string context
}

//Now how i can go back 5th string 4th string 3 2 1th string 
private void BtnBack_Click(object sender, RoutedEventArgs e)
{
  //Fift Forth Third Second First Observed string will show in the textbox
  // Reverse back previous string with sequence 
  TextBoxText.Text = context; // Will reverse/Go back in sequence 
}

How can i go back string

Even going forward forward string or and reverse back back . My english was not good enough to explain but if you are unable to understand what i was said please let me know

Answer 1

You need to keep references of the previous values. One approach is to keep a stack of strings where you push in the new value each time you hit BtnForward_Click() and pop (the most recent one) when you hit BtnBack_Click(). An example is given below:

    Stack context = new Stack();

    private void BtnForward_Click(object sender, RoutedEventArgs e)
    {
        // Here you would need to set the value of the Abcd based on your business logic
        context.Push(Abcd);
    }

    private void BtnBack_Click(object sender, RoutedEventArgs e)
    {
        try
        {
            TextBoxText.Text = context.Peek(); // gets the most recently entered value of the stack that has not been removed (popped)
            context.Pop();                
        }
        catch (InvalidOperationException exc)
        {
            // Nothing to go back to
        }
    }