Updating complex objects

I'm mainly looking at usage of Dapper, but in general, any comments relating SQL -> C# object mapping best practices would be appreciated.

I've got two super simple objects I'm working with:

public class Subcategory
{
    public Guid Id { get; set; }
    public Guid CategoryId { get; set; }
    public string Name { get; set; }
}

public class Category
{
    public Category()
    {
        Subcategories = new List();
    }

    public Guid Id { get; set; }
    public string Name { get; set; }
    public ICollection Subcategories { get; set; }
}

Id for both of them is set by the db on insert via T-SQL's newsequentialid().

I'm writing repository classes for each of the objects that conform to the following interface (actually implemented via an abstract class):

public interface IMaintanceRepository where T: class
{
    Guid Create(T toCreate);
    T Read(Guid id);
    T Update(T toUpdate);
    void Delete(Guid id);
}

Right now, I'm trying to write the Update method in the Category repository. I have the following written, but I'm not sure if it's the most performant Dapper code as written.

```
public override Category Update(Category toUpdate)
{
var deleteRemovedSubcategories = @"
DELETE FROM dbo.Subcategories
WHERE CategoryId = @Id
AND Id NOT IN @Ids";

var addNewSubcategories = @"
INSERT INTO dbo.Subcategories (CategoryId, Name)
VALUES (@CategoryId, @Name)";

var updateExistingSubcategories = @"
CREATE TABLE #subcategories (
Id uniqueidentifier NOT NULL,
CategoryId uniqueidentifier NOT NULL,
Name varchar(50) NOT NULL
);

INSERT INTO #subcategories VALUES (@Id, @CategoryId, @Name);

UPDATE s1
SET s1.CategoryId = s2.CategoryId, s1.Name = s2.Name
FROM dbo.Subcategories s1
INNER JOIN #subcategories s2
ON s1.Id = s2.Id;

DROP TABLE #subcategories;";

var updateCategory = @"

I was looking at what you had coded here

var deleteRemovedSubcategories = @"
    DELETE FROM dbo.Subcategories 
    WHERE CategoryId = @Id 
        AND Id NOT IN @Ids";

and it took me a minute to figure out exactly what the Where clause was filtering, what finally gave it away was the name of the C# variable deleteRemovedSubcategories. If it were possible I would change some of these column names and/or T-SQL variables so that it is more clear what you are saying here.

StackExchange Code Review Q#152016, answer score: 2