fix: High CPU usage in FluentDataGrid

[JamesNK]

🐛 Bug Report

I stress tested Aspire and had a grid with many rows that updated once a second. I noticed very high CPU usage. I profiled and found uncached usage of Expression.Compile().

Profile:

Likely offender:

fluentui-blazor/src/Core/Components/DataGrid/Columns/TemplateColumn.cs

Lines 26 to 27 in 4516f95

	protected internal override string? RawCellContent(TGridItem item)
	=> TooltipText?.Compile()(item);

Which is called from RenderRow:

fluentui-blazor/src/Core/Components/DataGrid/FluentDataGrid.razor

Lines 89 to 106 in 4516f95

	private void RenderRow(RenderTreeBuilder __builder, int rowIndex, TGridItem item)
	{
	var rowClass = RowClass?.Invoke(item) ?? null;
	var rowStyle = RowStyle?.Invoke(item) ?? null;
	Loading = false;
	<FluentDataGridRow @key="@(ItemKey(item))" GridTemplateColumns=@GridTemplateColumns aria-rowindex="@rowIndex" Class="@rowClass" Style="@rowStyle" TGridItem="TGridItem" Item="@item">
	@for (var colIndex = 0; colIndex < _columns.Count; colIndex++)
	{
	var col = _columns[colIndex];
	string? tooltip = col.Tooltip ? @col.RawCellContent(item) : null;
	<FluentDataGridCell GridColumn=@(colIndex+1) Class="@ColumnClass(col)" Style="@col.Style" @key="@col" TGridItem="TGridItem" Item="@item" title="@tooltip" aria-label="@tooltip">
	@((RenderFragment)(__builder => col.CellContent(__builder, item)))
	</FluentDataGridCell>
	}
	</FluentDataGridRow>
	}

💻 Repro or Code Sample

Create a big grid with tooltips. Have it update often.

🤔 Expected Behavior

Renders quickly.

😯 Current Behavior

Very high CPU usage.

💁 Possible Solution

Cache compiled expression.

🔦 Context

🌍 Your Environment

• OS & Device: [e.g. MacOS, iOS, Windows, Linux] on [iPhone 7, PC]
• Browser [e.g. Microsoft Edge, Google Chrome, Apple Safari, Mozilla FireFox]
• .NET and Fluent UI Blazor library Version [e.g. 8.0.2 and 4.4.1]

[JamesNK]

Can you reopen this? I think the current solution will create a dictionary for every combination of row type and property type. It would probably be better to have one dictionary for all expressions, and then cast the returned type. It's not as strongly typed, but will return memory usage.

Also, there are some other places where there is Expression.Compile that might need work to improve caching:

fluentui-blazor/src/Core/Components/DataGrid/Columns/PropertyColumn.cs

Lines 53 to 102 in 902bcc8

	if (_lastAssignedProperty != Property)
	{
	_lastAssignedProperty = Property;
	var compiledPropertyExpression = Property.Compile();
	if (!string.IsNullOrEmpty(Format))
	{
	// TODO: Consider using reflection to avoid having to box every value just to call IFormattable.ToString
	// For example, define a method "string Type<U>(Func<TGridItem, U> property) where U: IFormattable", and
	// then construct the closed type here with U=TProp when we know TProp implements IFormattable
	// If the type is nullable, we're interested in formatting the underlying type
	var nullableUnderlyingTypeOrNull = Nullable.GetUnderlyingType(typeof(TProp));
	if (!typeof(IFormattable).IsAssignableFrom(nullableUnderlyingTypeOrNull ?? typeof(TProp)))
	{
	throw new InvalidOperationException($"A '{nameof(Format)}' parameter was supplied, but the type '{typeof(TProp)}' does not implement '{typeof(IFormattable)}'.");
	}
	_cellTextFunc = item => ((IFormattable?)compiledPropertyExpression!(item))?.ToString(Format, null);
	}
	else
	{
	_cellTextFunc = item => compiledPropertyExpression!(item)?.ToString();
	}
	_sortBuilder = Comparer is not null ? GridSort<TGridItem>.ByAscending(Property, Comparer) : GridSort<TGridItem>.ByAscending(Property);
	}
	Func<TGridItem, string?>? compiledTooltipTextExpression = TooltipText?.Compile();
	_cellTooltipTextFunc = compiledTooltipTextExpression is not null
	? (item => compiledTooltipTextExpression(item)?.ToString())
	: _cellTextFunc;
	if (Property.Body is MemberExpression memberExpression)
	{
	if (Title is null)
	{
	PropertyInfo = memberExpression.Member as PropertyInfo;
	var daText = memberExpression.Member.DeclaringType?.GetDisplayAttributeString(memberExpression.Member.Name);
	if (!string.IsNullOrEmpty(daText))
	{
	Title = daText;
	}
	else
	{
	Title = memberExpression.Member.Name;
	}
	}
	}

Some research is probably needed into the best way to cache expressions. This seems like a common problem so there will be people who have solved it before.

[vnbaaij]

Expression and Compile logic has been removed from the TooltipText parameter and handling.