Update Part-10.md

docs/en/Tutorials/Part-10.md

@@ -1126,6 +1126,21 @@ protected override async Task OnInitializedAsync()
 
 * It is essential to call the `base.OnInitializedAsync()` since `AbpCrudPageBase` has some initialization code to be executed.
 
+Override the `OpenCreateModalAsync` method and adding the following code:
+
+````csharp
+protected override async Task OpenCreateModalAsync()
+    {
+        if (!authorList.Any())
+        {
+            throw new UserFriendlyException(message: L["AnAuthorIsRequiredForCreatingBook"]);
+        }
+        
+        await base.OpenCreateModalAsync();
+        NewEntity.AuthorId = authorList.First().Id;
+    }
+````
+
 The final `@code` block should be the following:
 
 ````csharp
@@ -1147,6 +1162,17 @@ The final `@code` block should be the following:
         await base.OnInitializedAsync();
         authorList = (await AppService.GetAuthorLookupAsync()).Items;
     }
+
+    protected override async Task OpenCreateModalAsync()
+    {
+        if (!authorList.Any())
+        {
+            throw new UserFriendlyException(message: L["AnAuthorIsRequiredForCreatingBook"]);
+        }
+        
+        await base.OpenCreateModalAsync();
+        NewEntity.AuthorId = authorList.First().Id;
+    }
 }
 ````
 
@@ -1156,7 +1182,6 @@ Finally, add the following `Field` definition into the `ModalBody` of the *Creat
 <Field>
     <FieldLabel>@L["Author"]</FieldLabel>
     <Select TValue="Guid" @bind-SelectedValue="@NewEntity.AuthorId">
-        <SelectItem TValue="Guid" Value="Guid.Empty">@L["PickAnAuthor"]</SelectItem>
         @foreach (var author in authorList)
         {
             <SelectItem TValue="Guid" Value="@author.Id">
@@ -1170,7 +1195,7 @@ Finally, add the following `Field` definition into the `ModalBody` of the *Creat
 This requires to add a new localization key to the `en.json` file:
 
 ````js
-"PickAnAuthor": "Pick an author"
+"AnAuthorIsRequiredForCreatingBook": "An author is required to create a book"
 ````
 
 You can run the application to see the *Author Selection* while creating a new book: