Visual webpart - The type or namespace name 'List' could not be found (are you missing a using directive or an assembly reference?)

Question

I'm trying to create Web Part properties. Below is my code :

using System;
using System.ComponentModel;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using Microsoft.SharePoint;
using Microsoft.SharePoint.WebControls;

namespace SP2010VisualWebPart.AmazingVisualWebPart
{
    [ToolboxItemAttribute(false)]
    public class AmazingVisualWebPart : WebPart
    {

        private PrettyColors _textColor = PrettyColors.Black;


        public PrettyColors textColor
        {
            get { return _textColor; }
            set { _textColor = value; }
        }


        private const string _ascxPath = @"~/_CONTROLTEMPLATES/SP2010VisualWebPart/AmazingVisualWebPart/AmazingVisualWebPartUserControl.ascx";


        private AmazingVisualWebPartUserControl userControlReference;

        protected override void CreateChildControls()
        {
            Control control = Page.LoadControl(_ascxPath);
            Controls.Add(control);


            userControlReference = (AmazingVisualWebPartUserControl)control;
            userControlReference.SetWebPartReference(this);
        }

        protected override void OnPreRender(EventArgs e)
        {
            base.OnPreRender(e);
            userControlReference.SetTextColor(this._textColor.ToString());
        }

        public override EditorPartCollection CreateEditorParts()
        {

            List<EditorPart> editorParts = new List<EditorPart>(1);
            EditorPart editorPart = new AmazingVisualEditorPart.AmazingVisualEditorPart();
            editorPart.ID = this.ID + "_EditorPart";
            editorParts.Add(editorPart);

            return new EditorPartCollection(base.CreateEditorParts(), editorParts);
        }
    }
}

Below is the error I am getting

The type or namespace name 'List' could not be found (are you missing a using directive or an assembly reference?)

How can i debug this?

Answer 1

Add using System.Collections.Generic; at the top of your code. You haven't imported the namespace.

http://msdn.microsoft.com/en-us/library/6sh2ey19.aspx

(Or, in VS2010, right click on the List<T> object, hover on resolve, and click "add using statement")