quote:

---

Msg 6522, Level 16, State 2, Line 1
A .NET Framework error occurred during execution of user-defined routine or aggregate "PercBytes":
System.NullReferenceException: Object reference not set to an instance of an object.
System.NullReferenceException:
at PercBytes.Terminate()

---

[Serializable]

[SqlUserDefinedAggregate(

    Format.UserDefined,        //use custom serialization to serialize the intermediate result
    IsInvariantToNulls = true,  //optimizer property
    IsInvariantToDuplicates = false, //optimizer property
    IsInvariantToOrder = false, //optimizer property
    MaxByteSize = 8000)        //maximum size in bytes of persisted value

]

public class PercBytes : IBinarySerialize
{
    private StringBuilder intermediateResult;
    private ArrayList items;

    public void Init()
    {
        this.intermediateResult = new StringBuilder();
        this.items = new ArrayList();
    }

    public void Accumulate(SqlString value)
    {
        if (value.IsNull)
        {
            this.items.Add("null");
        }
        else
        {
            this.items.Add(value);
        }
    }

    public void Merge(PercBytes other)
    {
        this.items.Add(other.items);
    }

    public int Terminate()
    {
        return items.Count;
    }

    public void Read(BinaryReader reader)
    {
        intermediateResult = new StringBuilder(reader.ReadString());
    }

    public void Write(BinaryWriter writer)
    {
        writer.Write(this.intermediateResult.ToString());
    }
}

CREATE ASSEMBLY CLRLib FROM 'G:\CLRLib.dll'

GO

create AGGREGATE PercBytes (@input nvarchar(max)) RETURNS int

  EXTERNAL NAME clrlib.PercBytes

GO

select dbo.PercBytes(BytesSent),App_ID from dbo.fact_runid_1(nolock)
and BytesSent != 0
group by App_ID