Is it wrong to use braces for variable scope purposes?

Question

I sometimes use braces to isolate a block of code to avoid using by mistake a variable later. For example, when I put several SqlCommands in the same method, I frequently copy-paste blocks of code, ending by mixing the names and executing twice some commands. Adding braces helps to avoid this situation, because using a wrong SqlCommand in a wrong place will result in an error. Here's an illustration:

Collection<string> existingCategories = new Collection<string>();

// Here a beginning of a block
{
    SqlCommand getCategories = new SqlCommand("select Title from Movie.Category where SourceId = @sourceId", sqlConnection, sqlTransaction);
    getCategories.Parameters.AddWithValue("@sourceId", sourceId);
    using (SqlDataReader categoriesReader = getCategories.ExecuteReader(System.Data.CommandBehavior.SingleResult))
    {
        while (categoriesReader.Read())
        {
            existingCategories.Add(categoriesReader["Title"].ToString());
        }
    }
}

if (!existingCategories.Contains(newCategory))
{
    SqlCommand addCategory = new SqlCommand("insert into Movie.Category (SourceId, Title) values (@sourceId, @title)", sqlConnection, sqlTransaction);

    // Now try to make a mistake and write/copy-paste getCategories instead of addCategory. It will not compile.
    addCategory.Parameters.AddWithValue("@sourceId", sourceId);
    addCategory.Parameters.AddWithValue("@title", newCategory);
    addCategory.ExecuteNonQuery();
}

Now, StyleCop displays a warning every time a block follows an empty line. On the other hand, not putting an empty line would make the code much harder to understand.

// Something like:
Collection<string> existingCategories = new Collection<string>();
{
    // Code here
}

// can be understood as (is it easy to notice that semicolon is missing?):
Collection<string> existingCategories = new Collection<string>()
{
    // Code here
}

So,

1. Is there something wrong in using braces to create blocks of code just for variable scope purposes?

2. If it's all right, how to make it more readable without violating StyleCop rules?

Answer 1

I don't think there's anything wrong with using braces purely to delimit scope - it can be quite useful at times.

Case in point - I came across a profiling library once that used Profile objects to time sections of code. These worked by measuring the time from their creation to destruction, and therefore worked best by being created on the stack and then being destroyed when they went out of scope, thus measuring the time spent in that particular scope. If you wanted to time something that didn't inherently have its own scope, then adding extra braces to define that scope was probably the best way to go.

As for readability, I can understand why StyleCop doesn't like it, but anyone with any experience in C/C++/Java/C#/... knows that a brace pair defines a scope, and it should be fairly evident that that's what you're trying to do.