Comments by Member 16239100

Member 16239100 25-Apr-24 14:27pm View

I think the Algorithm will be like:

When content is not SCrolling
1) During Mouse Move Draw the rectangle for Selection and iterate over each row to check what rows are intersecting with rectangle to make them selected otherwise unselect the rows if rectangle is not over them.

When content is AutoScrolling:
1) Keep drawing the rectangle and Whatever rows are intersecting select it. But the rows which are going out of view for them Keep a Flag like contentISautscrolling so dont deselect them.

Is it the right way?

Member 16239100 25-Apr-24 12:43pm View

Hi @Pete O'Hanlon how can i improve the solution which i have posted as answer. I think we need to change the selection Logic there as you have suggested. Here i am using RowMosueEnter events
to do the selection.

Member 16239100 25-Apr-24 12:33pm View

Deleted

// Variables to store selection rectangle info
Point startPoint;
Rectangle selectionRectangle;

// Mouse down event handler
private void DataGrid_MouseDown(object sender, MouseEventArgs e)
{
startPoint = e.GetPosition(null);

// Initialize the selection rectangle
selectionRectangle = new Rectangle
{
Stroke = Brushes.Black,
StrokeThickness = 1,
Opacity = 0.5
};

Canvas.SetLeft(selectionRectangle, startPoint.X);
Canvas.SetTop(selectionRectangle, startPoint.Y);

canvas.Children.Add(selectionRectangle);
}

// Mouse move event handler
private void DataGrid_MouseMove(object sender, MouseEventArgs e)
{
if (e.LeftButton == MouseButtonState.Pressed)
{
Point endPoint = e.GetPosition(null);

double x = Math.Min(endPoint.X, startPoint.X);
double y = Math.Min(endPoint.Y, startPoint.Y);

double width = Math.Abs(endPoint.X - startPoint.X);
double height = Math.Abs(endPoint.Y - startPoint.Y);

selectionRectangle.Width = width;
selectionRectangle.Height = height;

Canvas.SetLeft(selectionRectangle, x);
Canvas.SetTop(selectionRectangle, y);
}
}

// Mouse up event handler
private void DataGrid_MouseUp(object sender, MouseEventArgs e)
{
canvas.Children.Remove(selectionRectangle);

// Now iterate through your DataGrid cells and check for selection
foreach (DataGridRow row in dataGrid.Items)
{
foreach (DataGridColumn column in dataGrid.Columns)
{
var cell = GetCell(dataGrid, row.Item, column);
Point cellTopLeft = cell.PointToScreen(new Point(0, 0));
Point cellBottomRight = cell.PointToScreen(new Point(cell.ActualWidth, cell.ActualHeight));

// Check if the cell is within the selection rectangle
if (IsCellWithinSelection(cellTopLeft, cellBottomRight))
{
// Perform selection logic here
}
}
}
}

// Helper method to check if a cell is within the selection rectangle
private bool IsCellWithinSelection(Point topLeft, Point bottomRight)
{
double selectionLeft = Canvas.GetLeft(selectionRectangle);
double selectionTop = Canvas.GetTop(selectionRectangle);
double selectionRight = selectionLeft + selectionRectangle.Width;
double selectionBottom = selectionTop + selectionRectangle.Height;

return topLeft.X >= selectionLeft && topLeft.Y >= selectionTop
&& bottomRight.X <= selectionRight && bottomRight.Y <= selectionBottom;
}

// Helper method to get a DataGridCell from row and column
private DataGridCell GetCell(DataGrid grid, object item, DataGridColumn column)
{
DataGridRow row = (DataGridRow)grid.ItemContainerGenerator.ContainerFromItem(item);
if (row != null)
{
int columnIndex = grid.Columns.IndexOf(column);
if (columnIndex > -1)
{
DataGridCellsPresenter presenter = GetVisualChild<datagridcellspresenter>(row);
return (DataGridCell)presenter.ItemContainerGenerator.ContainerFromIndex(columnIndex);
}
}
return null;
}
Just to took the idea of code i took from AI and i think we should do selection during mouse move.

Member 16239100 25-Apr-24 11:17am View

Here how to handle the scrolling case where on autoscroll rectangle will not over the rows which are not visible as they scrolldown. How to keep them selected. That time the rectangle will move alongwith scollable content.

Member 16239100 11-Apr-24 9:33am View

it's not like your thoughts are not useful but i am not able to analyse like when to redraw the rectangle with fixed starting point and when to not. Can you please elaborate clearly. And since I am very new to this technology sometimes I might not understand what you are trying to convey.
Thanks for your time 😊

Member 16239100 11-Apr-24 9:06am View

I don't know what are you trying to say. Can you tell me did you really understood the problem or I have to rephrase the question for better understanding?
I am not able to analyse like when to redraw the rectangle with fixed starting point and when to not. Can you please elaborate clearly.

Member 16239100 11-Apr-24 8:27am View

here if you check on left click im keeping the startpoint of rectangle fixed and ending point is keep on changing during mouse move.
can you check my SelectItemsInRectangle function. I think if i everytime redraw rectangle by changing the start point then the rows below it will deselect or can you have some please suggest some better logic.

private void DataGrid_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{

//DependencyObject dep = (DependencyObject)e.OriginalSource;

//// Check if the mouse click is on the headers or scroll bars
//while (dep != null && dep != FileDataGrid)
//{
// if (dep is DataGridColumnHeader || dep is ScrollBar)
// {
// // Clicked on headers or scroll bars, do not initiate selection
// return;
// }

// dep = VisualTreeHelper.GetParent(dep);
//}

isleftbuttonpressed = true;
isSelecting = true;
selectionStartPoint = e.GetPosition(FileDataGrid);

adorner = new SelectionAdorner(FileDataGrid, selectionStartPoint);
var adornerLayer = AdornerLayer.GetAdornerLayer(FileDataGrid);
adornerLayer.Add(adorner);
adorner.SetStartPoint(selectionStartPoint);

}

private void DataGrid_PreviewMouseMove(object sender, MouseEventArgs e)
{
if (e.LeftButton == MouseButtonState.Pressed)
{

isleftbuttonpressed = true;
e.Handled = false;
}
if (isSelecting && adorner != null)
{
adorner.SetEndPoint(e.GetPosition(FileDataGrid));

var selectionRect = adorner.GetSelectionRect();
SelectItemsInRectangle(selectionRect, FileDataGrid, sender, e);
}

public Rect GetSelectionRect()
{
// double height = Math.Abs(endPoint.Y - startPoint.Y); // Calculate height
// selectionHeights.Add(height);
return new Rect(startPoint, endPoint);
}

private void SelectItemsInRectangle(Rect selectionRect, DataGrid dataGrid, object sender, MouseEventArgs e)
{

foreach (var item in dataGrid.Items)
{
var row = (DataGridRow)dataGrid.ItemContainerGenerator.ContainerFromItem(item);
if (row != null)
{
var rowBounds = GetRowBoundsRelativeToDataGrid(row, dataGrid);

// Check if the row intersects with the selection rectangle
if (selectionRect.IntersectsWith(rowBounds))
{
// Select the item and add it to the collection of selected items
row.IsSelected = true;

}
else
{
// If the item was previously selected but is not in the selection rectangle, deselect it
row.IsSelected = false;

}
}
}
}

Member 16239100 11-Apr-24 8:26am View

Deleted

here if you check on left click im keeping the startpoint of rectangle fixed and on mouse move and ending point is keep on changing during mouse move.
can you check my SelectItemsInRectangle function. I think if i everytime redraw rectangle by changing the start point then the rows below it will deselect or can you have some please suggest some better logic.

private void DataGrid_PreviewMouseMove(object sender, MouseEventArgs e)
{
if (e.LeftButton == MouseButtonState.Pressed)
{

isleftbuttonpressed = true;
e.Handled = false;
}
if (isSelecting && adorner != null)
{
adorner.SetEndPoint(e.GetPosition(FileDataGrid));

var selectionRect = adorner.GetSelectionRect();
SelectItemsInRectangle(selectionRect, FileDataGrid, sender, e);
}

public Rect GetSelectionRect()
{
// double height = Math.Abs(endPoint.Y - startPoint.Y); // Calculate height
// selectionHeights.Add(height);
return new Rect(startPoint, endPoint);
}

private void SelectItemsInRectangle(Rect selectionRect, DataGrid dataGrid, object sender, MouseEventArgs e)
{

foreach (var item in dataGrid.Items)
{
var row = (DataGridRow)dataGrid.ItemContainerGenerator.ContainerFromItem(item);
if (row != null)
{
var rowBounds = GetRowBoundsRelativeToDataGrid(row, dataGrid);

// Check if the row intersects with the selection rectangle
if (selectionRect.IntersectsWith(rowBounds))
{
// Select the item and add it to the collection of selected items
row.IsSelected = true;

}
else
{
// If the item was previously selected but is not in the selection rectangle, deselect it
row.IsSelected = false;

}
}
}
}

Member 16239100 11-Apr-24 8:23am View

Deleted

here if you check on left click im keeping the startpoint of rectangle fixed and on mouse move and ending point is keep on changing during mouse move.
can you check my SelectItemsInRectangle function. I think if i everytime redraw rectangle by changing the start point then the rows below it will deselect or can you have some please suggest some better logic.

private void DataGrid_PreviewMouseMove(object sender, MouseEventArgs e)
{
if (e.LeftButton == MouseButtonState.Pressed)
{

isleftbuttonpressed = true;
e.Handled = false;
}
if (isSelecting && adorner != null)
{
adorner.SetEndPoint(e.GetPosition(FileDataGrid));

var selectionRect = adorner.GetSelectionRect();
SelectItemsInRectangle(selectionRect, FileDataGrid, sender, e);
}

public Rect GetSelectionRect()
{
// double height = Math.Abs(endPoint.Y - startPoint.Y); // Calculate height
// selectionHeights.Add(height);
return new Rect(startPoint, endPoint);
}

private void SelectItemsInRectangle(Rect selectionRect, DataGrid dataGrid, object sender, MouseEventArgs e)
{

foreach (var item in dataGrid.Items)
{
var row = (DataGridRow)dataGrid.ItemContainerGenerator.ContainerFromItem(item);
if (row != null)
{
var rowBounds = GetRowBoundsRelativeToDataGrid(row, dataGrid);

// Check if the row intersects with the selection rectangle
if (selectionRect.IntersectsWith(rowBounds))
{
// Select the item and add it to the collection of selected items
row.IsSelected = true;

}
else
{
// If the item was previously selected but is not in the selection rectangle, deselect it
row.IsSelected = false;

}
}
}
}

Member 16239100 11-Apr-24 8:23am View

Deleted

private void DataGrid_PreviewMouseMove(object sender, MouseEventArgs e)
{
if (e.LeftButton == MouseButtonState.Pressed)
{

isleftbuttonpressed = true;
e.Handled = false;
}
if (isSelecting && adorner != null)
{
adorner.SetEndPoint(e.GetPosition(FileDataGrid));

var selectionRect = adorner.GetSelectionRect();
SelectItemsInRectangle(selectionRect, FileDataGrid, sender, e);
}

public Rect GetSelectionRect()
{
// double height = Math.Abs(endPoint.Y - startPoint.Y); // Calculate height
// selectionHeights.Add(height);
return new Rect(startPoint, endPoint);
}

private void SelectItemsInRectangle(Rect selectionRect, DataGrid dataGrid, object sender, MouseEventArgs e)
{

foreach (var item in dataGrid.Items)
{
var row = (DataGridRow)dataGrid.ItemContainerGenerator.ContainerFromItem(item);
if (row != null)
{
var rowBounds = GetRowBoundsRelativeToDataGrid(row, dataGrid);

// Check if the row intersects with the selection rectangle
if (selectionRect.IntersectsWith(rowBounds))
{
// Select the item and add it to the collection of selected items
row.IsSelected = true;

}
else
{
// If the item was previously selected but is not in the selection rectangle, deselect it
row.IsSelected = false;

}
}
}
}

here if you check on left click im keeping the startpoint of rectangle fixed and on mouse move and ending point is keep on changing during mouse move.
can you check my SelectItemsInRectangle function. I think if i everytime redraw rectangle by changing the start point then the rows below it will deselect or can you have some please suggest some better logic.

Member 16239100 11-Apr-24 7:54am View

so on mouse move i just need to update the end point or do i need to redraw the rectangle?

Member 16239100 11-Apr-24 6:01am View

No actually if you see win explorer use a selection rectangle to select the files and folders.

Member 16239100 11-Apr-24 5:31am View

Hi, @Jo_vb.net i think you did not understand the problem. The problem is the selection rectangle is not the part of the datagrid, its an adorner which is selecting the datagrid rows by hovering over it like we do in windows file explorer. Son here what is happening, the rectangle will remain fixed at one position during scroll as its not the part of the datagrid scrollviewer and the datagrid rows content will scroll up and down. You can see the visual representation here
https://stackoverflow.com/questions/78304588/selection-rectangle-not-moving-along-with-wpf-datagrid-content-during-scroll
You can see in the pic that selection rectangle is above the rows and its like its in the air and the content below it will scroll up and down and it will remain fixed. But in windows file explorer if you see, its the part of datagrid and it will scroll with datagrid content. So is there any way i can fix this problem.

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