在Windows Forms C＃中模拟降雪

Question

I'm quite new in C# and I want to creating something like falling snow (dots) in C# using Windows Forms.

I was already able to create the snowflakes at the top of the screen (I want to create new dot every 0,1s, at random x-position of Form and write down every snowflake's position into the List(Point) and with every Tick of timer (0,1s) I want the snowflake to change its position by 3px down and 1-3px right)

But I have the problem with refreshing the snowflakes positions. I don't know how to acces each snowflake in the List to Randomize its new position. I tried foreach, but it gives me error, that says I cannot change variable in foreach.

Example:

foreach (var snowflake in snowflakeList)            
            {
               snowflake.Y += 3;
               snowflake.X += moveRandom.Next(1, 4);
            }

Can anyone please tell me how can I divide List(Point) of snowflakes into invdividual snowflakes, so I could change position of every single dot separately?

Thank you :-)

Answer 1

The simplest way is just to use the index of the collection:

for (int i = 0; i < snowflakeList.Count; i++)            
{
    var snowflake = snowflakeList[i];
    snowflake.Y += 3;
    snowflake.X += moveRandom.Next(1, 4);
    snowflakeList[i] = snowflake;
}

Answer 2

As Andrews answer use a for loop, but as the list is of Points (a value type) you would need to reference the Point in the list directly rather than make a copy of it:

for (int i = 0; i < snowflakeList.Count; i++)            
{
    snowflakeList[i].Y += 3;
    snowflakeList[i].X += moveRandom.Next(1, 4);
}