Question

I am working on an ASP.NET MVC application.

I have a ViewModel class for which I am trying to maintain a count in order to generate div ids which are used in a view:

public class ViewModel {

    private static uint instanceCount;
    private readonly uint id;

    public ViewModel(){
        id = instanceCount++;
    }

    public uint DivId
    {
        get { return id; }
    }
}

Am I correct in thinking incrementing and assigning the static member is not threadsafe and thus not safe in a web application?

What is the best way to make this safe?

Thanks.

Answer 1

Am I correct in thinking incrementing and assigning the static member is not threadsafe and thus not safe in a web application?

Yes, you are correct into thinking this.

What is the best way to make this safe?

By synchronizing the access:

public class ViewModel
{
    private static uint instanceCount;
    private readonly uint id;
    private static object _syncRoot = new object();

    public ViewModel()
    {
        lock(_syncRoot)
        {
            id = instanceCount++;
        }
    }

    public uint DivId
    {
        get { return id; }
    }
}

or simply use a Guid:

public class ViewModel
{
    public ViewModel
    {
        DivId = string.Format("id_{0}", Guid.NewGuid());
    }

    public string DivId { get; private set; }
}