Optimized keyboard controls for XNA game - xna-4.0

Question

The code I am using for controlling the four-directional movement of the player's sprite in my 2D game is exhibiting some unwanted affection. I realize that this affection is because the if conditions that are first met will trump the later else ifs... So the directional affection my code shows now is: left > right > up > down.
What kind of affection I want is: the first direction pressed > the second direction pressed > the third direction pressed > the fourth direction pressed.
I also want it to remember what order the keypresses are in untill they're released.
Example:
I hold left, the sprite moves left.
I push up while still holding left, and the sprite immediately moves up.
I release up while still holding left, and the sprite resumes its movement left.
This memory should encompass all four directional keys so that the controls won't feel buggy if the user has "fat fingers".
This is the code I use for movement so far:
if (CurrentKeyboardState.IsKeyDown(Keys.Left) == true)
{
Speed.X = moveSpeed;
Direction.X = moveLeft;
}
else if (CurrentKeyboardState.IsKeyDown(Keys.Right) == true)
{
Speed.X = moveSpeed;
Direction.X = moveRight;
}
else if (CurrentKeyboardState.IsKeyDown(Keys.Up) == true)
{
Speed.Y = moveSpeed;
Direction.Y = moveUp;
}
else if (CurrentKeyboardState.IsKeyDown(Keys.Down) == true)
{
Speed.Y = moveSpeed;
Direction.Y = moveDown;
}
I am thinking I could use a List and just put the direction pressed (left, right, up, down) as strings into the list if it isn't already in the list, and then always check what the latest item in the list is to decide what directio to move. And of course remove the strings when the corresponding keys are released. Would this be a good way of solving it?
Here is my attempt on this:
if (currentKeyboardState.IsKeyDown(Keys.Left))
{
if (!keyDownList.Contains("left"))
{
keyDownList.Add("left");
System.Diagnostics.Debug.WriteLine("left inserted");
}
}
else if (oldKeyboardState.IsKeyDown(Keys.Left))
{
keyDownList.Remove("left");
System.Diagnostics.Debug.WriteLine("left removed");
}
if (currentKeyboardState.IsKeyDown(Keys.Right))
{
if (!keyDownList.Contains("right"))
{
keyDownList.Add("right");
System.Diagnostics.Debug.WriteLine("right added");
}
}
else if (oldKeyboardState.IsKeyDown(Keys.Right))
{
keyDownList.Remove("right");
System.Diagnostics.Debug.WriteLine("right removed");
}
if (currentKeyboardState.IsKeyDown(Keys.Up))
{
if (!keyDownList.Contains("up"))
{
keyDownList.Add("up");
System.Diagnostics.Debug.WriteLine("up added");
}
}
else if (oldKeyboardState.IsKeyDown(Keys.Up))
{
keyDownList.Remove("up");
System.Diagnostics.Debug.WriteLine("up removed");
}
if (currentKeyboardState.IsKeyDown(Keys.Down))
{
if (!keyDownList.Contains("down"))
{
keyDownList.Add("down");
System.Diagnostics.Debug.WriteLine("down added");
}
}
else if (oldKeyboardState.IsKeyDown(Keys.Down))
{
keyDownList.Remove("down");
System.Diagnostics.Debug.WriteLine("down removed");
}
try
{
if (keyDownList[keyDownList.Count-1].Contains("left"))
{
//move left
speed.X = moveSpeed;
direction.X = moveLeft;
}
else if (keyDownList[keyDownList.Count-1].Contains("right"))
{
//move right
speed.X = moveSpeed;
direction.X = moveRight;
}
else if (keyDownList[keyDownList.Count-1].Contains("up"))
{
//move up
speed.Y = moveSpeed;
direction.Y = moveUp;
}
else if (keyDownList[keyDownList.Count-1].Contains("down"))
{
//move down
speed.Y = moveSpeed;
direction.Y = moveDown;
}
}
catch (Exception e)
{
}
I had some problems with it initially, but it seems to work fine now with the exception of it generating exceptions (A first chance exception of type 'System.ArgumentOutOfRangeException' occurred in mscorlib.dll) while my sprite is standing still. Any tips on how to stop that?
I'm not just looking for a solution that works, but for something durable and efficient that feels rock solid and professional, so discussion on the topic is more than welcome.

Answer 1

Durable, efficient, rock solid, etc. it may not be, but what you're saying with your if/else if block there is that you're only interested in one keystate per frame, when I don't think that's the case.
What happens if you try:
if (CurrentKeyboardState.IsKeyDown(Keys.Down) & !CurrentKeyboardState.IsKeyDown(Keys.Up))
{
Speed.Y = moveSpeed;
Direction.Y = moveDown;
}
if (CurrentKeyboardState.IsKeyDown(Keys.Up) & !CurrentKeyboardState.IsKeyDown(Keys.Down))
{
Speed.Y = moveSpeed;
Direction.Y = moveUp;
}
And repeat similar for left and right. By testing mutual exclusivity between opposing directions, you keep yourself from adding to and subtracting from direction in the same frame. Also, by using separate conditions instead of an if/elseif chain, you allow the possibility to process Left + Up in the same frame.