improved dynamic CSS handling

Oqtane.Client/Shared/Interop.cs

@@ -57,6 +57,21 @@ namespace Oqtane.Shared
             }
         }
 
+        public Task RemoveCSS(string filepattern)
+        {
+            try
+            {
+                jsRuntime.InvokeAsync<string>(
+                    "interop.removeCSS",
+                    filepattern);
+                return Task.CompletedTask;
+            }
+            catch
+            {
+                return Task.CompletedTask;
+            }
+        }
+
         public ValueTask<string> GetElementByName(string name)
         {
             try

Oqtane.Client/Shared/ThemeBuilder.razor

@@ -1,6 +1,8 @@
 @using Oqtane.Shared
 @using Oqtane.Modules
+@using Microsoft.JSInterop
 @namespace Oqtane.Shared
+@inject IJSRuntime jsRuntime
 
 @DynamicComponent
 
@@ -28,4 +30,12 @@
             }
         };
     }
+
+    protected override async Task OnParametersSetAsync()
+    {
+        // remove any custom CSS
+        var interop = new Interop(jsRuntime);
+        await interop.RemoveCSS("Themes/");
+        await interop.RemoveCSS("Modules/");
+    }
 }