compilera C#

Lyckas inte compilera förljande kod

using Microsoft.SharePoint;

using System;

namespace test
{

    class TestEventReceiver : SPItemEventReceiver
    {

        public override void ItemUpdated(SPItemEventProperties properties)
        {

            DisableEventFiring(); // in ValidateItem it will fire an event, so disable here

            ValidateItem(properties);

        }

        public override void ItemAdded(SPItemEventProperties properties)
        {

            DisableEventFiring(); // in ValidateItem it will fire an event, so disable here

            ValidateItem(properties);

        }

        protected bool ValidateItem(SPItemEventProperties properties)
        {

            SPSite siteV = null;

            SPWeb webV = null;

            if (properties.ListItemId > 0 && properties.ListId != Guid.Empty)
            {

                try
                {

                    siteV = new SPSite(properties.WebUrl);

                    webV = siteV.OpenWeb();

                    SPList spList = webV.Lists.GetList(properties.ListId, false);

                    SPListItem Item = spList.GetItemById(properties.ListItemId);

                    // The internal number ist stored in _UIVersion

                    //    1 for V0.1

                    //  512 for V1.0

                    //  513 for V1.1

                    // 1024 for V2.0

                    //Item["WSSVNumber"] = Item["_UIVersion"];

                    // I'm using the string value

                    Item["WSSVersion"] = Item["_UIVersionString"];

                    Item.SystemUpdate();

                }

                catch // You will run into an exception in case the Column does not exist
                {

                    // Put your exception code here

                }

            }

            return true;

        }

    }

}

får bla. följande felmeddelande:

Error 1 The type or namespace name 'SharePoint' does not exist in the namespace 'Microsoft' (are you missing an assembly reference?) \\Server1\Users\Felix\My Documents\Visual Studio 2008\Projects\FeatureTest.dll\FeatureTest\Class1.cs 1 17 FeatureTest

hittar ingen referens till Sharepoint
vad göra?