MudDataGrid: Add inline row editing

[mmaestro16]

Description

This PR adds support for inline row editing to MudDataGrid, providing a new edit mode where individual rows can be edited in place without opening a dialog. This feature complements the existing Cell and Form edit modes.

What's Changed

New Inline Enum Value
• Added Inline to the DataGridEditMode enum
• When a row enters edit mode, only that row displays input controls
• All other rows continue to display plain text

New Public API Methods

• IsEditingItem(T item) - Checks if a specific item is currently being edited in inline mode
• CommitInlineEditAsync() - Commits inline edits, validates changes, and persists to the source item
• Internal GetEditingItemOrSource(T item) - Returns the editing copy if the item is being edited, otherwise returns the source item

Enhanced CellContext

• New IsEditing property - Indicates whether the row containing the cell is currently being edited
• Updated CommitEditingItemAsync - Now works with inline mode to commit and exit edit mode
• Properly distinguishes between the editing copy and source item

Updated Cell Rendering Logic

• Cells now check for inline edit mode and render appropriate controls
• EditTemplate is used when the row is being edited
• Regular CellTemplate or formatted values are shown otherwise
• Proper handling of editable vs. non-editable columns during inline editing

Key Features

• Manual Trigger: Works with EditTrigger.Manual via custom action buttons in a TemplateColumn
• Validation Support: Respects CommittedItemChanges callback for validation - return DataGridEditFormAction.KeepOpen to prevent commit
• Event Callbacks: Triggers StartedEditingItem, CanceledEditingItem, CommittedItemChanges, and CommittedItemChanged appropriately
• Single Row Editing: Only one row can be edited at a time
• Isolated Changes: Edits are made to a cloned copy; canceling discards all changes
• No Dialog: Unlike Form mode, inline editing keeps users in the grid context

Usage Example

<MudDataGrid T="Element" 
             Items="@elements" 
             ReadOnly="false"
             EditMode="DataGridEditMode.Inline"
             EditTrigger="DataGridEditTrigger.Manual"
             CommittedItemChanges="@ValidateChanges">
    <Columns>
        <PropertyColumn Property="x => x.Name">
            <EditTemplate>
                <MudTextField @bind-Value="context.Item.Name" 
                              Margin="Margin.Dense" 
                              Variant="Variant.Text" />
            </EditTemplate>
        </PropertyColumn>
        
        <TemplateColumn>
            <CellTemplate>
                @if (context.IsEditing)
                {
                    <MudIconButton Icon="@Icons.Material.Filled.Check" 
                                   OnClick="@context.Actions.CommitEditingItemAsync" />
                    <MudIconButton Icon="@Icons.Material.Filled.Close" 
                                   OnClick="@context.Actions.CancelEditingItemAsync" />
                }
                else
                {
                    <MudIconButton Icon="@Icons.Material.Outlined.Edit" 
                                   OnClick="@context.Actions.StartEditingItemAsync" />
                }
            </CellTemplate>
        </TemplateColumn>
    </Columns>
</MudDataGrid>

Tests

Added comprehensive unit tests covering:
• Starting edit mode and showing edit controls
• Canceling edits and restoring original values
• Committing edits and persisting changes
• Validation with KeepOpen behavior
• Validation failure preventing commits
• Validation failure then success flow
• IsEditing property state management
• Only edited row showing inputs
• Direct API calls (CommitInlineEditAsync(), CancelEditingItemAsync)
• No dialog opened in inline mode

Test components created:
• DataGridInlineEditTest.razor - Comprehensive inline editing scenarios
• DataGridInlineEditValidationTest.razor - Validation-focused testing

Screenshots

Checklist:

• I've read the contribution guidelines
• My code follows the style of this project
• I've added or updated relevant unit tests

[mmaestro16]

@versile2 please have a look. I would like to know if I can count on this solution in my project.

[versile2]

I can promise you in either scenario it won't be fast, we all have our hand full for reviews. As to if it will be accepted I will let you know, we'll talk to the team and make sure it's something we can support moving forward.

V

[Phen-Ro]

Personally I am looking forward to this review and eventual merge. I was trying to hunt down how to allowed row-level edit mode without manual workarounds when I stumbled across this PR. For what it's worth, you will have guaranteed users of this new feature.

[versile2]

I have gotten no dissenting opinions, so I've queued this up for review.

[versile2]

Thanks for working on this. I think the inline edit direction is useful, but there are a couple of compatibility/behavior problems here that should be fixed before merge.

Blocking: cell edit no longer raises StartedEditingItem before the value changes

In Cell.cs, StringValueChangedAsync and NumberValueChangedAsync now set the property directly and then call CommitItemChangesAsync.

Before this change, the cell edit path called BeginCellEditAsync(_item) first. That initialized the editing source item, cloned the row, and raised StartedEditingItem before mutation. Consumers using DataGridEditMode.Cell can currently use that callback to snapshot pre-edit state.

This PR removes that ordering, so the callback semantics regress. The cell-edit path should still begin the edit and raise StartedEditingItem before applying the changed value.

Blocking: public API source break in CellContext<T> / CellActions

CellContext<T> replaces the existing public two-argument constructor with a three-argument constructor, and CellActions now has a new public required member.

That breaks consumer code that constructs these public types directly. Please keep the existing constructor overload and avoid adding a new required member to the public nested type. The new source item plumbing can be added without forcing existing callers to change.

Should fix: Selected and Open use the edited clone instead of the source row

CellContext.Selected and CellContext.Open still check Item, but inline edit now uses a cloned editing item while selection and hierarchy state are tracked against the original source row.

That means templates using context.Selected or context.Open can temporarily see the wrong value while the row is being edited. These should use the source item instead.

Cleanup: trailing whitespace

git diff origin/dev...HEAD --check currently fails on trailing whitespace in the PR diff, including the inline row editing example/test files and MudDataGrid.razor.

-- Comment / Review / Code handled by AI
-- Codebringer for versile2
-- Approved by versile2

[mmaestro16]

I merged code to latest dev branch and did required changes. Please check again.

[mmaestro16]

I hope now is all good.

[versile2]

Awesome work, thank you!
LGTM

[danielchalmers]

Thanks!