fullstackhero/dotnet-starter-kit · error · CustomException

Another category with name

Error message

Another category with name '{command.Name}' already exists.

What it means

UpdateCategory checks whether any other category already uses the resulting Slug; if so it throws CustomException with 409 Conflict, using the name in the message because slug is derived from name. It enforces unique category slugs at the application level.

Solutions

1. Choose a different, unique category name.
2. If duplicates are legitimate, disambiguate the name (add a qualifier) so the slug differs.
3. Refresh the category list to confirm the conflicting name, then decide which to keep.
4. Consider surfacing slug uniqueness in the form validator before submission.

Example fix

// before
await api.updateCategory({ id, name: 'Electronics' }); // conflicts

// after
await api.updateCategory({ id, name: 'Electronics Outlet' }); // unique slug

const others = (await api.listCategories()).items.filter(c => c.id !== editingId);
const slug = slugify(payload.name);
if (others.some(c => c.slug === slug)) {
  return formError('A category with this name already exists.');
}

try { await api.updateCategory(payload); }
catch (e) { if (e.status === 409) formError('Name already in use — pick another'); else throw e; }

When it happens

Trigger: PUT update renaming a category to a name whose generated slug collides with another existing category's slug (excluding itself via c.Id != category.Id).

Common situations: Two categories named alike (e.g. 'Shoes (sale)' and 'Shoes sale' slug-collide); renaming a category to match an existing one; race where another user created the same name between page load and save.

Understand the failure class

Background: "already exists" / EEXIST / FileAlreadyExistsException: what the 'file already exists' error means and how to fix it — this error's family across 37 libraries.

Related errors

• A product with name ' ' already exists.
• Another product with name
• A brand with name ' ' already exists.
• Another brand with name
• A category with name

AI-assisted analysis of fullstackhero/dotnet-starter-kit@3f2959e683 (2026-09-15). Data as JSON: /api/errors/7f0818a453edb3ef. Report an issue: GitHub.

Appendix: source

Thrown at src/Modules/Catalog/Modules.Catalog/Features/v1/Categories/UpdateCategory/UpdateCategoryCommandHandler.cs:59

                        (IEnumerable<string>?)null,
                        HttpStatusCode.BadRequest);
                }
                cursor = await dbContext.Categories
                    .Where(c => c.Id == cur)
                    .Select(c => c.ParentCategoryId)
                    .FirstOrDefaultAsync(cancellationToken)
                    .ConfigureAwait(false);
            }
        }

        category.Update(command.Name, command.Description, command.ParentCategoryId);

        bool slugTaken = await dbContext.Categories
            .AnyAsync(c => c.Slug == category.Slug && c.Id != category.Id, cancellationToken)
            .ConfigureAwait(false);
        if (slugTaken)
        {
            throw new CustomException(
                $"Another category with name '{command.Name}' already exists.",
                (IEnumerable<string>?)null,
                HttpStatusCode.Conflict);
        }

        await dbContext.SaveChangesAsync(cancellationToken).ConfigureAwait(false);
        return category.Id;
    }
}

View on GitHub (pinned to 3f2959e683)