float AddAngle(float original, float angle){
    var r = original + angle;
    if(r < 0) r = 360 + r;
    if(r > 360) r -= 360;
    return r;
}

var playerAngle = 0f;

Console.WriteLine(AddAngle(playerAngle, 45));
Console.WriteLine(AddAngle(playerAngle, 135));
Console.WriteLine(AddAngle(playerAngle, 225));
Console.WriteLine(AddAngle(playerAngle, 315));