SelectExtended: Add the ability to display additional content (#455)

* SelectExtended: Add the ability to display additional content within the popover above the list

* SelectExtended: rename AdditionalContent to StaticContent

* SelectExtended: add an option to show the StaticContent at the bottom of the list

Author: jneufferrpm

CodeBeam.MudBlazor.Extensions/Components/SelectExtended/MudSelectExtended.razor

@@ -94,15 +94,20 @@
                                     }
                                 }
                             </div>
-                            
+
                         </DataVisualiser>
 
                         <ChildContent>
-                            
+
                         </ChildContent>
                     </MudInputExtended>
 
-				<MudPopover Open="@_isOpen" MaxHeight="@MaxHeight" AnchorOrigin="@AnchorOrigin" TransformOrigin="@TransformOrigin" Class="@PopoverClass" RelativeWidth="@RelativeWidth">
+                    <MudPopover Open="@_isOpen" MaxHeight="@MaxHeight" AnchorOrigin="@AnchorOrigin" TransformOrigin="@TransformOrigin" Class="@PopoverClass" RelativeWidth="@RelativeWidth">
+                        @if (StaticContent != null && !ShowStaticContentAtEnd)
+                        {
+                            @StaticContent(this)
+                        }
+
                         <CascadingValue Value="@this" IsFixed="true">
                             <MudListExtended @ref="@_list" T="T" @bind-SelectedValue="@Value" Style="@($"overflow-y:auto; max-height: {MaxHeight}px")" @bind-SelectedValues="@SelectedValues" @bind-SelectedItem="@SelectedListItem" @bind-SelectedItems="@SelectedListItems"
                                              Clickable="true" Color="@Color" Dense="@Dense" ItemCollection="@ItemCollection" Virtualize="@Virtualize" Padding="@EnablePopoverPadding" DisableSelectedItemStyle="@EnableSelectedItemStyle"
@@ -113,6 +118,11 @@
                                 @ChildContent
                             </MudListExtended>
                         </CascadingValue>
+
+                        @if (StaticContent != null && ShowStaticContentAtEnd)
+                        {
+                            @StaticContent(this)
+                        }
                     </MudPopover>
                 </InputContent>
             </MudInputControl>

CodeBeam.MudBlazor.Extensions/Components/SelectExtended/MudSelectExtended.razor.cs

@@ -107,6 +107,20 @@ public MudSelectExtended()
         [Category(CategoryTypes.FormComponent.ListBehavior)]
         public RenderFragment? ChildContent { get; set; }
 
+        /// <summary>
+        /// Optional additional content to display above the list within the popover.
+        /// </summary>
+        [Parameter]
+        [Category(CategoryTypes.FormComponent.Appearance)]
+        public RenderFragment<MudSelectExtended<T>>? StaticContent { get; set; }
+
+        /// <summary>
+        /// Whether to show <see cref="StaticContent"/> at the bottom of the popover.
+        /// </summary>
+        [Parameter]
+        [Category(CategoryTypes.FormComponent.Appearance)]
+        public bool ShowStaticContentAtEnd { get; set; }
+
         /// <summary>
         /// Optional presentation template for items
         /// </summary>