Problem with arraylist assignment

[djkno3]

((Rectangle)mySquares[i]).X = ((Rectangle)mySquares[i-1]).X; I have an ArrayList of Rectangles and would like to update the X co-ordinate with the old one but this assignment generates a compiler error "The left-hand side of an assignment must be a variable, property or indexer" yet the left hand side of this IS a property. Is there a reason for this? do I have to extract/assign the x co-ordinates in a for loop?

[Rob Graham]

If this is not already in a for loop, then how is the current value of i determined? in any event, it will fail for i=0 since there is no element whose index = -1. Perhaps we need a to see just a wee bit more of your code in order to help?;):suss:

[djkno3]

for (i = mySquares.Count - 1; i > 0; i--) { ((Rectangle)mySquares[i]).X = ((Rectangle)mySquares[i-1]).X; ((Rectangle)mySquares[i]).Y = ((Rectangle)mySquares[i-1]).Y; } I'm trying to update the x,y co-ordinates of the rectangles in the arrary in a Timer.Tic() method. it tells me that my left operand has to be a property but is Rectangle.X not a property?

[Burt Harris]

Interesting, try this: for (int i = mySquares.Count - 1; i > 0; i--) { Rectangle r1 = (Rectangle)mySquares[i]; Rectangle r2 = (Rectangle)mySquares[i-1]; r1.X = r2.X; r1.Y = r2.Y; }Burt Harris

[Richard Deeming]

Rectangle is a struct, so that probably won't work anyway, since you're changing the coordinates of an unboxed copy of your rectangle. Try something like:

for (i = mySquares.Count - 1; i > 0; i--)
{
mySquares[i] = new Rectangle(
((Rectangle)mySquares[i-1]).Location,
((Rectangle)mySquares[i]).Size);
}

---

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

[James T Johnson]

Burt Harris (msft) wrote: Rectangle r1 = (Rectangle)mySquares[i]; Rectangle r2 = (Rectangle)mySquares[i-1]; Unfortunately that won't work either. The problem is that Rectangle is a value type so the modifications you are doing are being done to the unboxed value which is discarded. Instead, you should create a new Rectangle object and place it back in the collection.

for (int i = mySquares.Count - 1; i > 0; i--)
{
Rectangle r1 = (Rectangle)mySquares[i];
Rectangle r2 = (Rectangle)mySquares[i-1];

mySquares\[i\] = new Rectangle(r2.X, r2.Y, 
    r1.Width, r1.Height);

}

[Edit]I should have posted this sooner instead of catching up on CP, Richard beat me to it :P[/Edit] James - out of order -

[djkno3]

Thanks everyone for your replies it is working now (Well at least the assignment problem I had :laugh: