Question

Guys, I’m trying to convert something from C# to VB.NET and I’m having trouble finding an equivlent in VB.NET to C#’s yield keyword. I realize ‘yield’ is not a convertable keyword to VB.NET, so can someone please show me how I would implement this code in VB.NET. I got all of it converted over except for the implemented GetEnumerator() function. It is simply a class that implements CollectionBase and IEnumerable (to make it LINQ worthy):

[Serializable()]
public partial class Customers : CollectionBase,    System.Collections.Generic.IEnumerable<BusinessLayer.Customer> 
{

    public new System.Collections.Generic.IEnumerator<BusinessLayer.Customer> GetEnumerator()
    {
        foreach (BusinessLayer.Customer Cust in this.List)
        {
            yield return Cust;
        }
    }

    public Customers()
    {

    }

    public Customers(DataRowCollection datarows) : this()
    {
        this.Load(datarows);
    }
    protected void Load(DataRowCollection dataRows)
{
    foreach (DataRow dr in dataRows) {
        this.Add(new Customer(dr));
    }
}

public Customer this[int index] {
    get { return (Customer)base.InnerList[index]; }
    set { base.InnerList[index] = value; }
}

public int Add(Customer val)
{
    return base.InnerList.Add(val);
}
}

Thanks in advance for any help!

Answer 1

Because you cannot use the yield keyword, you will have to implement GetEnumerator() another way. What you can do is return the enumerator of the List from CollectionBase. However, because this is an IList and not an IList<T>, you will have to cast it (you can use the Cast<T>() extension method from Linq for this). Your C# code then becomes:

public IEnumerator<BusinessLayer.Customer> GetEnumerator()
{
    return InnerList.Cast<BusinessLayer.Customer>().GetEnumerator();
}

This gives the same result, but behaves in a slightly different way (with regards to no longer using the delayed execution of yield).

In VB.Net, GetEnumerator() would be:

Public Function GetEnumerator() As IEnumerator(Of BusinessLayer.Customer)
    Return InnerList.Cast(Of BusinessLayer.Customer)().GetEnumerator()
End Function

The rest of your code should translate directly to VB.Net.