We Keep Coding

How to delete image created with code and how to interact with it at all

I am working on a game. For this game i create around 200 images in a box 20x10.
My problem is that pressing 1 button creates them a lot of times which garbages the Memory, which i want to avoid. So i created a little if/else function which is supposed to check wether the images were created or not. In case they weren't, code creates them, but if they were, the code should delete them, and i have no idea how to delete code generated images or how to interract with them at all.
public void GameStart(bool load = false)
{
Random rnd = new Random();
Pause.IsEnabled = true;
Save.IsEnabled = true;
Shuffle.IsEnabled = true;
byte datasave = 0;
int[,] TileID = new int[20,10];
for(int i = 0; i < 20; i++)
{
for(int j = 0; j < 10; j++)
{
if(TileID[i,j] != 0)
{
datasave = 1;
}
TileID[i, j] = rnd.Next(1,9);
CreateImage(i, j, TileID[i,j], datasave);
}
}
}
public void CreateImage(int a, int b, int TileID, byte datainfo)
{
if(datainfo != 0)
{
Image image = new Image();
image.Width = 40;
image.Height = 40;
image.Name = $"Tile{a}{b}";
image.HorizontalAlignment = System.Windows.HorizontalAlignment.Center;
image.VerticalAlignment = System.Windows.VerticalAlignment.Center;
image.Margin = new Thickness(-1000 + 80 * a, -200 + 80 * b, 0, 0);
string way = #"C:\Users\ignat\Desktop\Игра\Images\";
image.Source = new BitmapImage(new Uri(way + $"icon{TileID}.jpg", UriKind.Absolute));
Grid.Children.Add(image);
}
else
{
CreateImage(a, b, TileID, datainfo);
}

how can I split a panel to clickable segments in c# winform?

I am trying to simulate a LED display board with c# . I need a control which contains 1536 clickable controls to simulate LEDs (96 in width and 16 in Height). I used a panel named pnlContainer for this and user will add 1536 tiny customized panels at runtime. These customized panels should change their color by click event at runtime. Everything works . But adding this number of tiny panels to the container takes long time ( about 10 secs). What is your suggestion to solve this issue? Any tips are appreciated.
this is my custome panel:
public partial class LedPanel : Panel
{
public LedPanel()
{
InitializeComponent();
}
protected override void OnPaint(PaintEventArgs pe)
{
base.OnPaint(pe);
}
protected override void OnMouseDown(MouseEventArgs e)
{
if (e.Button == MouseButtons.Left)
{
if (this.BackColor == Color.Black)
{
this.BackColor = Color.Red;
}
else
{
this.BackColor = Color.Black;
}
}
}
}
and this is piece of code which adds tiny panels to the pnlContainer :
private void getPixels(Bitmap img2)
{
pnlContainer.Controls.Clear();
for (int i = 0; i < 96; i++)
{
for (int j = 0; j < 16; j++)
{
Custom_Controls.LedPanel led = new Custom_Controls.LedPanel();
led.Name = i.ToString() + j.ToString();
int lWidth = (int)(pnlContainer.Width / 96);
led.Left = i * lWidth;
led.Top = j * lWidth;
led.Width = led.Height = lWidth;
if (img2.GetPixel(i, j).R>numClear.Value)
{
led.BackColor = Color.Red;
}
else
{
led.BackColor = Color.Black;
}
led.BorderStyle = BorderStyle.FixedSingle;
pnlContainer.Controls.Add(led);
}
}
}
Is there any better approach or better control instead of panelto do this?

I agree with what #TaW recommends. Don't put 1000+ controls on a form. Use some sort of data structure, like an array to keep track of which LEDs need to be lit and then draw them in the Paint event of a Panel.
Here's an example. Put a Panel on a form and name it ledPanel. Then use code similar to the following. I just randomly set the values of the boolean array. You would need to set them appropriately in response to a click of the mouse. I didn't include that code, but basically you need to take the location of the mouse click, determine which array entry needs to be set (or unset) and then invalidate the panel so it will redraw itself.
public partial class Form1 : Form
{
//set these variables appropriately
int matrixWidth = 96;
int matrixHeight = 16;
//An array to hold which LEDs must be lit
bool[,] ledMatrix = null;
//Used to randomly populate the LED array
Random rnd = new Random();
public Form1()
{
InitializeComponent();
ledPanel.BackColor = Color.Black;
ledPanel.Resize += LedPanel_Resize;
//clear the array by initializing a new one
ledMatrix = new bool[matrixWidth, matrixHeight];
//Force the panel to repaint itself
ledPanel.Invalidate();
}
private void LedPanel_Resize(object sender, EventArgs e)
{
//If the panel resizes, then repaint.
ledPanel.Invalidate();
}
private void button1_Click(object sender, EventArgs e)
{
//clear the array by initializing a new one
ledMatrix = new bool[matrixWidth, matrixHeight];
//Randomly set 250 of the 'LEDs';
for (int i = 0; i < 250; i++)
{
ledMatrix[rnd.Next(0, matrixWidth), rnd.Next(0, matrixHeight)] = true;
}
//Make the panel repaint itself
ledPanel.Invalidate();
}
private void ledPanel_Paint(object sender, PaintEventArgs e)
{
//Calculate the width and height of each LED based on the panel width
//and height and allowing for a line between each LED
int cellWidth = (ledPanel.Width - 1) / (matrixWidth + 1);
int cellHeight = (ledPanel.Height - 1) / (matrixHeight + 1);
//Loop through the boolean array and draw a filled rectangle
//for each one that is set to true
for (int i = 0; i < matrixWidth; i++)
{
for (int j = 0; j < matrixHeight; j++)
{
if (ledMatrix != null)
{
//I created a custom brush here for the 'off' LEDs because none
//of the built in colors were dark enough for me. I created it
//in a using block because custom brushes need to be disposed.
using (var b = new SolidBrush(Color.FromArgb(64, 0, 0)))
{
//Determine which brush to use depending on if the LED is lit
Brush ledBrush = ledMatrix[i, j] ? Brushes.Red : b;
//Calculate the top left corner of the rectangle to draw
var x = (i * (cellWidth + 1)) + 1;
var y = (j * (cellHeight + 1) + 1);
//Draw a filled rectangle
e.Graphics.FillRectangle(ledBrush, x, y, cellWidth, cellHeight);
}
}
}
}
}
private void ledPanel_MouseUp(object sender, MouseEventArgs e)
{
//Get the cell width and height
int cellWidth = (ledPanel.Width - 1) / (matrixWidth + 1);
int cellHeight = (ledPanel.Height - 1) / (matrixHeight + 1);
//Calculate which LED needs to be turned on or off
int x = e.Location.X / (cellWidth + 1);
int y = e.Location.Y / (cellHeight + 1);
//Toggle that LED. If it's off, then turn it on and if it's on,
//turn it off
ledMatrix[x, y] = !ledMatrix[x, y];
//Force the panel to update itself.
ledPanel.Invalidate();
}
}
I'm sure there can be many improvements to this code, but it should give you an idea on how to do it.

#Chris and #user10112654 are right.
here is a code similar to #Chris but isolates the displaying logic in a separate class. (#Chris answered your question when I was writing the code :))))
just create a 2D array to initialize the class and pass it to the Initialize method.
public class LedDisplayer
{
public LedDisplayer(Control control)
{
_control = control;
_control.MouseDown += MouseDown;
_control.Paint += Control_Paint;
// width and height of your tiny boxes
_width = 5;
_height = 5;
// margin between tiny boxes
_margin = 1;
}
private readonly Control _control;
private readonly int _width;
private readonly int _height;
private readonly int _margin;
private bool[,] _values;
// call this method first of all to initialize the Displayer
public void Initialize(bool[,] values)
{
_values = values;
_control.Invalidate();
}
private void MouseDown(object sender, MouseEventArgs e)
{
var firstIndex = e.X / OuterWidth();
var secondIndex = e.Y / OuterHeight();
_values[firstIndex, secondIndex] = !_values[firstIndex, secondIndex];
_control.Invalidate(); // you can use other overloads of Invalidate method for the blink problem
}
private void Control_Paint(object sender, PaintEventArgs e)
{
if (_values == null)
return;
e.Graphics.Clear(_control.BackColor);
for (int i = 0; i < _values.GetLength(0); i++)
for (int j = 0; j < _values.GetLength(1); j++)
Rectangle(i, j).Paint(e.Graphics);
}
private RectangleInfo Rectangle(int firstIndex, int secondIndex)
{
var x = firstIndex * OuterWidth();
var y = secondIndex * OuterHeight();
var rectangle = new Rectangle(x, y, _width, _height);
if (_values[firstIndex, secondIndex])
return new RectangleInfo(rectangle, Brushes.Red);
return new RectangleInfo(rectangle, Brushes.Black);
}
private int OuterWidth()
{
return _width + _margin;
}
private int OuterHeight()
{
return _height + _margin;
}
}
public class RectangleInfo
{
public RectangleInfo(Rectangle rectangle, Brush brush)
{
Rectangle = rectangle;
Brush = brush;
}
public Rectangle Rectangle { get; }
public Brush Brush { get; }
public void Paint(Graphics graphics)
{
graphics.FillRectangle(Brush, Rectangle);
}
}
this is how it's used in the form:
private void button2_Click(object sender, EventArgs e)
{
// define the displayer class
var displayer = new LedDisplayer(panel1);
// define the array to initilize the displayer
var display = new bool[,]
{
{true, false, false, true },
{false, true, false, false },
{false, false, true, false },
{true, false, false, false }
};
// and finally
displayer.Initialize(display);
}

How to render tiles efficiently using Graphics.Draw?

I am currently making a tile-based game in c#, but every time I draw the tiles it uses a lot of CPU, and as the tiles get bigger(if i make the game full screen) it consumes even more.
This is my Tile class:
public class Tiles
{
//PRIVATE :
//variabiles
private int XPosition, YPosition;
private Image Texture;
private bool Colidable;
private int SizeW = 32;
private int SizeH = 32;
private Resizer resizer = new Resizer();
//methods
//PUBLIC :
//variabiles
//methods
//CONSTRUCTOR
public Tiles(int _x,int _y,Image _i, int _sW = 32, int _sH = 32, bool _c = false)
{
XPosition = _x;//set position X
YPosition = _y;//set position Y
SizeW = _sW;
SizeH = _sH;
Texture = resizer.ResizeImage(_i, SizeW, SizeH) ;// set texture
Colidable = _c;//set if the tile is colidable,default : false
resizer = null;
}
//DRAW METHOD
//gets graphics object to draw on, adn draws at the position of the tile
public void Draw(Graphics _g)
{
_g.DrawImage(this.Texture, this.XPosition, this.YPosition);
}
//GET PRIVATE MEBERS
//returns if the tile is colidable
public bool getColidable()
{
return this.Colidable;
}
}
and this is how I draw the tiles:
private void DrawMap(Graphics _g)
{
//CALLS THE DRAW METHOD OF EACH TILE
for (int i = 0; i < MAP_WIDTH; i++)
{
for (int j = 0; j < MAP_HEIGHT; j++)
{
Tile[i, j].Draw(_g);
}
}
}
bool TilesUpdate = false;
private void _Window_Paint(object sender, PaintEventArgs e)
{
e.Graphics.Clear(Color.Black);
if (isGameRunning)
{
DrawMap(e.Graphics);
}
else
{
FullRezolutionBtn.Draw(e.Graphics);
BigRezolutionBtn.Draw(e.Graphics);
NormalRezolutionBtn.Draw(e.Graphics);
}
}
private void Update_Tick(object sender, EventArgs e)
{
Invalidate();
}
I want to mention that the map is 20 x 20 tiles and it's cosuming around 50% of the cpu when it's fullscreen.

As I mentioned in the comments, the direction should be to do less painting. One way is to invalidate and paint portions of the drawing canvas only when something related to that portion changes. Windows itself does such optimization for controls/windows.
Here is an example. Look how Gadget class invalidates it's rectangle when some property changes. Then during the paint, only rectangles that intersect with e.ClipRectange are drawn. This highly reduces the number of the drawing operations.
using System;
using System.Drawing;
using System.Windows.Forms;
namespace Samples
{
class Gadget
{
public readonly Control Canvas;
public Gadget(Control canvas) { Canvas = canvas; }
private Rectangle bounds;
public Rectangle Bounds
{
get { return bounds; }
set
{
if (bounds == value) return;
// NOTE: Invalidate both old and new rectangle
Invalidate();
bounds = value;
Invalidate();
}
}
private Color color;
public Color Color
{
get { return color; }
set
{
if (color == value) return;
color = value;
Invalidate();
}
}
public void Invalidate()
{
Canvas.Invalidate(bounds);
}
public void Draw(Graphics g)
{
using (var brush = new SolidBrush(color))
g.FillRectangle(brush, bounds);
}
}
static class Program
{
[STAThread]
static void Main()
{
Application.EnableVisualStyles();
Application.SetCompatibleTextRenderingDefault(false);
var form = new Form { WindowState = FormWindowState.Maximized };
int rows = 9, cols = 9;
var gadgets = new Gadget[rows, cols];
var rg = new Random();
Color[] colors = { Color.Yellow, Color.Blue, Color.Red, Color.Green, Color.Magenta };
int size = 64;
var canvas = form;
for (int r = 0, y = 8; r < rows; r++, y += size)
for (int c = 0, x = 8; c < cols; c++, x += size)
gadgets[r, c] = new Gadget(canvas) { Color = colors[rg.Next(colors.Length)], Bounds = new Rectangle(x, y, size, size) };
int paintCount = 0, drawCount = 0;
canvas.Paint += (sender, e) =>
{
paintCount++;
for (int r = 0; r < rows; r++)
{
for (int c = 0; c < cols; c++)
{
if (e.ClipRectangle.IntersectsWith(gadgets[r, c].Bounds))
{
gadgets[r, c].Draw(e.Graphics);
drawCount++;
}
}
}
form.Text = $"Paint:{paintCount} Draw:{drawCount} of {(long)paintCount * rows * cols}";
};
var timer = new Timer { Interval = 100 };
timer.Tick += (sender, e) =>
{
gadgets[rg.Next(rows), rg.Next(cols)].Color = colors[rg.Next(colors.Length)];
};
timer.Start();
Application.Run(form);
}
}
}

Not sure how your resizer class works. i think there is problem when you re-size every image every time.
Texture = resizer.ResizeImage(_i, SizeW, SizeH) ;// set texture
i would replace above line like this
Texture = _i;// set texture but do not resize image now
at the same time update the Draw Function of Tile like below.
public void Draw(Graphics _g)
{
//now specify the location and size of the image.
_g.DrawImage(Texture , new Rectangle(this.XPosition, this.YPosition, SizeW, SizeH));
}
hopefully it should improve the performance.
if it flicker then you can use Double Buffer

How can I instantiate large number of buttons in Windows Forms?

I'm developing a theatre reservation software. I'm using Windows Forms, the seats is represented by a 2-dimensioned array. And I draw the buttons as following:
public void DrawSeats()
{
// pnl_seats is a Panel
pnl_seats.Controls.Clear();
// Here I store all Buttons instance, to later add all buttons in one call (AddRange) to the Panel
var btns = new List<Control>();
// Suspend layout to avoid undesired Redraw/Refresh
this.SuspendLayout();
for (int y = 0; y < _seatZone.VerticalSize; y++)
{
for (int x = 0; x < _seatZone.HorizontalSize; x++)
{
// Check if this seat exists
if (IsException(x, y))
continue;
// Construct the button with desired properties. SeatSize is a common value for every button
var btn = new Button
{
Width = SeatSize,
Height = SeatSize,
Left = (x * SeatSize),
Top = (y * SeatSize),
Text = y + "" + x,
Tag = y + ";" + x, // When the button clicks, the purpose of this is to remember which seat this button is.
Font = new Font(new FontFamily("Microsoft Sans Serif"), 6.5f)
};
// Check if it is already reserved
if (ExistsReservation(x, y))
btn.Enabled = false;
else
btn.Click += btn_seat_Click; // Add click event
btns.Add(btn);
}
}
// As said before, add all buttons in one call
pnl_seats.Controls.AddRange(btns.ToArray());
// Resume the layout
this.ResumeLayout();
}
But already with a seat zone of 20 by 20 (400 buttons), it spent almost 1 minute to draw it, and in debug I checked that the lack of performance, is the instantiation of the buttons.
There is a way to make it faster? Perhaps disable all events during the instatiation or another lightweight Control that has the Click event too?
UPDATE:
lbl was a test, the correct is btn, sorry.
UPDATE 2:
Here is the IsException and ExistsReservations methods:
private bool IsException(int x, int y)
{
for (var k = 0; k < _seatsExceptions.GetLength(0); k++)
if (_seatsExceptions[k, 0] == x && _seatsExceptions[k, 1] == y)
return true;
return false;
}
private bool ExistsReservation(int x, int y)
{
for (var k = 0; k < _seatsReservations.GetLength(0); k++)
if (_seatsReservations[k, 0] == x && _seatsReservations[k, 1] == y)
return true;
return false;
}

Suppose that you change your arrays for reservations and exclusions to
public List<string> _seatsExceptions = new List<string>();
public List<string> _seatsReservations = new List<string>();
you add your exclusions and reservations in the list with something like
_seatsExceptions.Add("1;10");
_seatsExceptions.Add("4;19");
_seatsReservations.Add("2;5");
_seatsReservations.Add("5;5");
your checks for exclusions and reservations could be changed to
bool IsException(int x, int y)
{
string key = x.ToString() + ";" + y.ToString();
return _seatsExceptions.Contains(key);
}
bool ExistsReservation(int x, int y)
{
string key = x.ToString() + ";" + y.ToString();
return _seatsReservations.Contains(key);
}
of course I don't know if you are able to make this change or not in your program. However consider to change the search on your array sooner or later.
EDIT I have made some tests, and while a virtual grid of 20x20 buttons works acceptably well (31 millisecs 0.775ms on average), a bigger one slows down noticeably. At 200x50 the timing jumps to 10 seconds (1,0675 on average). So perhaps a different approach is needed. A bound DataGridView could be a simpler solution and will be relatively easy to handle.

I also won't use such a myriad of controls to implement such a thing. Instead you should maybe create your own UserControl, which will paint all the seats as images and reacts on a click event.
To make it a little easier for you i created such a simple UserControl, that will draw all the seats and reacts on a mouse click for changing of the state. Here it is:
public enum SeatState
{
Empty,
Selected,
Full
}
public partial class Seats : UserControl
{
private int _Columns;
private int _Rows;
private List<List<SeatState>> _SeatStates;
public Seats()
{
InitializeComponent();
this.DoubleBuffered = true;
_SeatStates = new List<List<SeatState>>();
_Rows = 40;
_Columns = 40;
ReDimSeatStates();
MouseUp += OnMouseUp;
Paint += OnPaint;
Resize += OnResize;
}
public int Columns
{
get { return _Columns; }
set
{
_Columns = Math.Min(1, value);
ReDimSeatStates();
}
}
public int Rows
{
get { return _Rows; }
set
{
_Rows = Math.Min(1, value);
ReDimSeatStates();
}
}
private Image GetPictureForSeat(int row, int column)
{
var seatState = _SeatStates[row][column];
switch (seatState)
{
case SeatState.Empty:
return Properties.Resources.emptySeat;
case SeatState.Selected:
return Properties.Resources.choosenSeat;
default:
case SeatState.Full:
return Properties.Resources.fullSeat;
}
}
private void OnMouseUp(object sender, MouseEventArgs e)
{
var heightPerSeat = Height / (float)Rows;
var widthPerSeat = Width / (float)Columns;
var row = (int)(e.X / widthPerSeat);
var column = (int)(e.Y / heightPerSeat);
var seatState = _SeatStates[row][column];
switch (seatState)
{
case SeatState.Empty:
_SeatStates[row][column] = SeatState.Selected;
break;
case SeatState.Selected:
_SeatStates[row][column] = SeatState.Empty;
break;
}
Invalidate();
}
private void OnPaint(object sender, PaintEventArgs e)
{
var heightPerSeat = Height / (float)Rows;
var widthPerSeat = Width / (float)Columns;
e.Graphics.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality;
e.Graphics.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic;
e.Graphics.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.HighQuality;
e.Graphics.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
for (int row = 0; row < Rows; row++)
{
for (int column = 0; column < Columns; column++)
{
var seatImage = GetPictureForSeat(row, column);
e.Graphics.DrawImage(seatImage, row * widthPerSeat, column * heightPerSeat, widthPerSeat, heightPerSeat);
}
}
}
private void OnResize(object sender, System.EventArgs e)
{
Invalidate();
}
private void ReDimSeatStates()
{
while (_SeatStates.Count < Rows)
_SeatStates.Add(new List<SeatState>());
if (_SeatStates.First().Count < Columns)
foreach (var columnList in _SeatStates)
while (columnList.Count < Columns)
columnList.Add(SeatState.Empty);
while (_SeatStates.Count > Rows)
_SeatStates.RemoveAt(_SeatStates.Count - 1);
if (_SeatStates.First().Count > Columns)
foreach (var columnList in _SeatStates)
while (columnList.Count > Columns)
columnList.RemoveAt(columnList.Count - 1);
}
}
This will currently draw forty rows and columns (so there are 800 seats) and you can click on each seat to change its state.
Here are the images i used:
EmtpySeat:
ChoosenSeat:
FullSeat:
If you anchor this control and resize it or you click on a seat to change its state there can be some minor lacking for the repainting if you further increase the number of rows or columns, but that is still somewhere far below one second. If this still hurts you, you have to improve the paint method and maybe check the ClipRectangle property of the paint event and only paint the really needed parts, but that's another story.

Rather than using actual button controls, just draw the image of the seats then when the user clicks on a seat translate the mouse X,Y coordinates to determine which seat was clicked. This will be more efficient. Of course, the drawback is that you have to write the method to translate x,y coordinates to a seat, but that really isn't that difficult.

EDIT; it has been pointed out to me this will not work in Windows Forms!
Well, you are Sequentially working through it.
if one iteration costs 1 sec, the full process will take 400*1 in time.
Perhaps you should try and make a collection of your objects, and process it 'parallel'.
try the .Net framework (4 and above) 'parallel foreach' method:
http://msdn.microsoft.com/en-s/library/system.threading.tasks.parallel.foreach(v=vs.110).aspx
edit: so, if you have a list buttonnames, you can say
buttonNames.ForEach(x=>CreateButton(x));
while your CreateButton() method is as following:
private Button CreateButton(string nameOfButton) { Button b = new
Button(); b.Text = nameOfButton; //do whatever you want...
return b; }

List Operations without ForLoops

I have a class with the following members:
X
Y
Width
Height
One can create a rectangle with these parameters.
Now my problem is I have a list of this class, List<MyClass>.
I need to compare each object of the list with all the remaining objects in such a way that if the currentObject.Location(X, Y) falls in the rectangle(X, Y, Width, Height) of the other object, I need to delete the other object from the list.
I implemented it with for loops.
But the major problem is: performance.
My minimum list count is 300000.
Is there any procedure to improve the performance for this task uisng any of the .Net versions including LINQ?
`public class RectBase
{
private int _rectId;
private PointF _rectLocation;
private SizeF _rectSize;
public RectBase()
{
_rectId = -911;
_rectLocation = new PointF(0, 0);
_rectSize = new SizeF(0, 0);
}
public RectBase(int id, PointF loc, SizeF size)
{
_rectId = id;
_rectLocation = loc;
_rectSize = size;
}
public bool IsIntersected(RectBase otherRectObject)
{
RectangleF currentRect = new RectangleF(_rectLocation, _rectSize);
if (currentRect.Contains(otherRectObject.RectLocation))
return true;
else
return false;
}
public int RectId
{
get { return _rectId; }
set { _rectId = value; }
}
public PointF RectLocation
{
get { return _rectLocation; }
set { _rectLocation = value; }
}
public SizeF RectSize
{
get { return _rectSize; }
set { _rectSize = value; }
}
}
public class RectProcessor
{
List<RectBase> _rectList;
int maxCount = 300000;
public RectProcessor()
{
_rectList = new List<RectBase>();
FillList();
}
private void FillList()
{
// Adding the items to the list with dummy values
for (int i = 0; i < maxCount; i++)
{
int id = i+1;
PointF loc = new PointF(id, id);
SizeF sz = new SizeF(id, id);
RectBase obj = new RectBase(id, loc, sz);
_rectList.Add(obj);
}
}
private void RemoveIntersectedObjects()
{
List<RectBase> filteredList = new List<RectBase>();
bool isIntersected = false;
for (int i = 0; i < maxCount; i++)
{
for (int j = 0; j < maxCount; j++)
{
if (_rectList[i].IsIntersected(_rectList[j]))
{
isIntersected = true;
break;
}
}
if (!isIntersected)
{
filteredList.Add(_rectList[i]);
}
isIntersected = false;
}
}
}
`

The problem isn't eliminating for loops, at least in the way that you're thinking of it. Rewriting this in LINQ is just going to hide the for loops but they'll still be there. And that's the fundamental problem. Your algorithm, as written, is O(n^2) and that's why you see a ridiculous explosion in time as you go from 20,000 elements to 300,000 elements. You're doing 400,000,000 comparisons in the first case, and 90,000,000,000 in the second case and it will continue to grow like O(n^2).
So, the question you really want to ask is: is there an algorithm with time complexity better than O(n^2) for this problem?
Frankly, I don't know the answer to that question. I suspect that the answer is no: you can't know if a point is contained in some rectangle without comparing it to all the rectangles, and you have to inspect all the points. But maybe there's a clever way to do it such as computing the convex hull of all the rectangles and use that somehow?
This problem is an example of the field of computational geometry.