CRM 2011:插件 - 无法加载文件或程序集“Microsoft.Xrm.Client”

我希望构建一个相当简单的插件，用于计算使用的"单位"数量和剩余数量。我有两个自定义条目bc_learninglicences & bc_llbalance，插件 - 在创建bc_llbalance时触发，另一个用于更新。

bc_llbalance: Contains
    bc_learninglicense (Look up field on bc_learninglicences / bc_name)
    bc_units (units that are used by this record)
bc_learninglicences: Contains 
    bc_name
    bc_unitsquantity (This is set to the total qty of units)
    bc_unitsused (this needs to inherit the sum of "bc_units" on "bc_llbalance")
    bc_unitsremaining ( simply bc_unitsquantity - bc_unitsused )

好的，所以我包含了显然尚未完成的代码，因为我只是想弄清楚如何让bc_unitsused继承总和......此代码生成时没有错误。但是CRM错误：

插件意外异常（执行）：学习许可证。学习许可证：System.IO.FileNotFound异常：无法加载文件或程序集 'Microsoft.Xrm.Client，版本=5.0.9690.2165

我

有一个很短的期限来构建它，因为系统即将上线，但是我无法继续处理我不明白的这个错误......

在这一点上，无论是帮助错误还是代码/解决方案，都将不胜感激，因为我落后于这个项目的时间框架。

p.s 我是 CRM 2011 开发的新手，只有几周/很少的项目经验。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Xrm.Sdk;
using Microsoft.Xrm.Sdk.Query;
using Microsoft.Xrm.Sdk.Messages;
using System.Text.RegularExpressions;
using System.ServiceModel;
namespace LearningLicenses
{
    public class LearningLicenses : IPlugin
    {
        public void Execute(IServiceProvider serviceProvider)
        {
            try
            {
                // Obtain the execution context from the service provider.
                Microsoft.Xrm.Sdk.IPluginExecutionContext context = (Microsoft.Xrm.Sdk.IPluginExecutionContext)
                    serviceProvider.GetService(typeof(Microsoft.Xrm.Sdk.IPluginExecutionContext));
                //Extract the tracing service for use in debugging sandboxed plug-ins.
                ITracingService tracingService =
                    (ITracingService)serviceProvider.GetService(typeof(ITracingService));
                if (context.InputParameters.Contains("Target") &&
                        context.InputParameters["Target"] is Entity)
                 {
                     // Obtain the target entity from the input parmameters.
                     Entity entity = (Entity)context.InputParameters["Target"];
                IOrganizationServiceFactory serviceFactory = (IOrganizationServiceFactory)serviceProvider.GetService(typeof(IOrganizationServiceFactory));
                IOrganizationService service = serviceFactory.CreateOrganizationService(context.UserId);
                EntityReference a = (EntityReference)entity.Attributes["bc_learninglicense"];// ((EntityReference)targetEntity.Attributes["bc_learninglicense"]).Id;

                if (entity.LogicalName == "bc_llbalance")
                        try
                        {  
                            //fetchxml to get the sum total of estimatedvalue
                            string value_sum = string.Format(@"         
                    <fetch distinct='false' mapping='logical' aggregate='true'> 
                        <entity name='bc_llbalance'>
                            <attribute name='bc_units' alias='units_sum' aggregate='sum' />
                               <filter type='and'>
                                <condition attribute='bc_learninglicense' operator='eq' value='{0}' uiname='' 
                               </filter>
                        </entity>
                    </fetch>", a.Id);
                            FetchExpression fetch = new FetchExpression(value_sum);
                            EntityCollection value_sum_result = service.RetrieveMultiple(fetch);
                            var TotalValue = "";
                            // decimal TotalValue = 0;
                            foreach (var c in value_sum_result.Entities)
                            {
                                TotalValue = ((string)((AliasedValue)c["value_sum"]).Value);
                            }
                            Entity llc = new Entity("bc_learninglicences");
                            llc.Id = a.Id;
                            llc.Attributes.Add("bc_unitsused", TotalValue);
                            service.Update(llc);
                        }
                        catch (FaultException ex)
                        {
                            throw new InvalidPluginExecutionException("An error occurred in the plug-in.", ex);
                        }
                }
            }
            catch (FaultException ex)
            {
                throw new InvalidPluginExecutionException("An error occurred in the plug-in.", ex);
            }
        }
    }
 }

THE ERROR : 
Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=5.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: Unexpected exception from plug-in (Execute): LearningLicenses.LearningLicenses: System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.Xrm.Client, Version=5.0.9690.2165, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.Detail: 
<OrganizationServiceFault xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/xrm/2011/Contracts">
  <ErrorCode>-2147220956</ErrorCode>
  <ErrorDetails xmlns:d2p1="http://schemas.datacontract.org/2004/07/System.Collections.Generic" />
  <Message>Unexpected exception from plug-in (Execute): LearningLicenses.LearningLicenses: System.IO.FileNotFoundException: Could not load file or assembly 'Microsoft.Xrm.Client, Version=5.0.9690.2165, Culture=neutral, PublicKeyToken=31bf3856ad364e35' or one of its dependencies. The system cannot find the file specified.</Message>
  <Timestamp>2013-01-22T10:09:22.0275105Z</Timestamp>
  <InnerFault i:nil="true" />
  <TraceText>
[LearningLicenses: LearningLicenses.LearningLicenses]
[c1b35170-c563-e211-8c6d-b499bafd5e5b: LearningLicenses.LearningLicenses: Create of bc_llbalance]

</TraceText>
</OrganizationServiceFault>