Add function for setting sheet active.

src/BlazorDatasheet.SharedPages/Pages/Index.razor

@@ -6,6 +6,7 @@
 @using BlazorDatasheet.Core.Validation
 @using System.Drawing
 @using BlazorDatasheet.Core.Commands.Data
+@using BlazorDatasheet.Events
 
 <PageTitle>Index</PageTitle>
 
@@ -43,6 +44,7 @@
     <button @onclick="@SortSelectionDesc">Sort Desc</button>
     <button @onclick="@SortSelectionAsc">Sort ASc</button>
     <button @onclick="@(() => Sheet.SetFormat(Sheet.Selection.Regions, new CellFormat() { NumberFormat = "C2" }))">Currency</button>
+    <button @onclick="@(() => _datasheet.SetActiveAsync(true))">Set sheet active</button>
 </div>
 
 <div>

src/BlazorDatasheet/Datasheet.razor.cs

@@ -96,7 +96,7 @@ public partial class Datasheet : SheetComponentBase
     public bool CanUserInsertRows { get; set; } = true;
 
     /// <summary>
-    /// If set to true, the user can insert columns using the context menu.
+    /// If set to true, the user can insert columns using the context menu.f
     /// </summary>
     [Parameter]
     public bool CanUserInsertCols { get; set; } = true;
@@ -134,6 +134,11 @@ public partial class Datasheet : SheetComponentBase
 
     [Parameter] public bool ShowFormulaDependents { get; set; }
 
+    /// <summary>
+    /// Fired when the Datasheet becomes active or inactive (able to receive keyboard inputs).
+    /// </summary>
+    [Parameter] public EventCallback<SheetActiveEventArgs> OnSheetActiveChanged { get; set; }
+
     /// <summary>
     /// Exists so that we can determine whether the sheet has changed
     /// during parameter set
@@ -529,15 +534,15 @@ private void HandleCellMouseOver(object? sender, SheetPointerEventArgs args)
         this.UpdateSelectingEndPosition(args.Row, args.Col);
     }
 
-    private Task<bool> HandleWindowMouseDown(MouseEventArgs e)
+    private async Task<bool> HandleWindowMouseDown(MouseEventArgs e)
     {
         bool changed = IsDataSheetActive != IsMouseInsideSheet;
-        IsDataSheetActive = IsMouseInsideSheet;
+        await SetActiveAsync(IsMouseInsideSheet);
 
         if (changed)
             StateHasChanged();
 
-        return Task.FromResult(false);
+        return false;
     }
 
     private Task<bool> HandleWindowMouseUp(MouseEventArgs arg)
@@ -812,4 +817,17 @@ private RenderFragment GetIconRenderFragment(string? cellIcon)
             return rf;
         return _ => { };
     }
+
+    /// <summary>
+    /// Set the datasheet as active, which controls whether the sheet is ready to receive keyboard input events.
+    /// </summary>
+    /// <param name="value"></param>
+    public async Task SetActiveAsync(bool value = true)
+    {
+        if(value == IsDataSheetActive)
+            return;
+
+        IsDataSheetActive = value;
+        await OnSheetActiveChanged.InvokeAsync(new SheetActiveEventArgs(this, value));
+    }
 }

src/BlazorDatasheet/Events/SheetActiveEventArgs.cs

@@ -0,0 +1,13 @@
+namespace BlazorDatasheet.Events;
+
+public class SheetActiveEventArgs
+{
+    public Datasheet DataSheet { get;  }
+    public bool IsActive { get; }
+
+    public SheetActiveEventArgs(Datasheet dataSheet, bool isActive)
+    {
+        DataSheet = dataSheet;
+        IsActive = isActive;
+    }
+}