Client Object Model in Visual Webpart

Question

Hi
I am new to Client Object Model.I've to create a visual web part in SharePoint 2013 via Client Object Model using
SandBoxed solution.
i did following.
1-Created empty sharepoint project
2-added two dlls for Client Object Model in the project
Microsoft.SharePoint.Client
Microsoft.SharePoint.Client.Runtime
3-in the visual webpart .ascx file i just created asp label as  below
<asp:Label ID="label1" runat="server"></asp:Label>
4- in the visual webpart .cs file i write a client object model code to show title items in the label from the "Test" list as below.
5-when i deploy the code it deploys successfully,but when i try to insert this web-part on to the page it shows errors
as below.
Please tell me what am i doing wrong.Urgent help required.

Answer 1

Yes,deployed as sandbox solution.Actually i want to create a visual webpart in Sharepoint 2013 using Client Object Model. How can i do this,i followed below steps.
1-Created empty sharepoint project
2-added two dlls for Client Object Model in the project
Microsoft.SharePoint.Client
Microsoft.SharePoint.Client.Runtime
3-in the visual webpart .ascx file i just created asp label as  below
<asp:Label ID="label1" runat="server"></asp:Label>
4- in the visual webpart .cs file i write a client object model code to show title items in the label from the "Test" list as below.
using Microsoft.SharePoint.Client;
using System;
using System.ComponentModel;
using System.Web.UI.WebControls.WebParts;
namespace SharePointProject2.VisualWebPart1
    [ToolboxItemAttribute(false)]
    public partial class VisualWebPart1 : WebPart
        // Uncomment the following SecurityPermission attribute only when doing Performance Profiling on a farm solution
        // using the Instrumentation method, and then remove the SecurityPermission attribute when the code is ready
        // for production. Because the SecurityPermission attribute bypasses the security check for callers of
        // your constructor, it's not recommended for production purposes.
        // [System.Security.Permissions.SecurityPermission(System.Security.Permissions.SecurityAction.Assert, UnmanagedCode = true)]
        public VisualWebPart1()
        protected override void OnInit(EventArgs e)
            base.OnInit(e);
            InitializeControl();
        protected void Page_Load(object sender, EventArgs e)
            ClientContext context = new ClientContext("http://spsiteURL");
            List testList = context.Web.Lists.GetByTitle("Test");
            CamlQuery query = CamlQuery.CreateAllItemsQuery(100);
            ListItemCollection items = testList.GetItems(query);
            context.Load(items);
            context.ExecuteQuery();
            foreach (ListItem listItem in items)
                label1.Text = label1.Text + ", " + listItem["Title"];
If this is not the correct way then how can i  use client object model to get sharepoint list items.Please mention.