序列中包含一个以上的元素 [英] Sequence contains more than one element

问题描述

我在通过LINQ的霎那型RhsTruck的名单，让他们展示一些问题。

RhsTruck只是有性质在品牌，型号，序列等... RhsCustomer具有属性客户名称，CustomerAddress，等等...

我不断收到错误序列包含多个元素。有任何想法吗？难道我处理这个错误的方式？

 公共RhsCustomer GetCustomer（字符串customerNumber之）
{
    使用（RhsEbsDataContext上下文=新RhsEbsDataContext（））
    {
        RhsCustomer RC =（从x在context.custmasts
                          其中，x.kcustnum == customerNumber之
                          选择新RhsCustomer（）
                        {
                            客户名称= x.custname，
                            CustomerAddress = x.custadd +，+ x.custcity
                            CustomerPhone = x.custphone，
                            CustomerFax = x.custfax
                        }）的SingleOrDefault（）。
        返回RC;
    }
}

公开名单＆LT; RhsTruck＆GT; GetEquipmentOwned（RhsCustomer卡斯特）
{
    使用（RhsEbsDataContext上下文=新RhsEbsDataContext（））
    {
        VAR卡车=（从米context.mkpops
                      加入c在context.custmasts
                        在m.kcustnum等于c.kcustnum
                      其中，m.kcustnum == cust.CustomerNumber
                      选择新RhsTruck
                    {
                        使= m.kmfg，
                        模型= m.kmodel，
                        串行= m.kserialnum，
                        EquipID = m.kserialno1，
                        IsRental = FALSE
                    }）了ToList（）。
        返回卡车;
    }
}

保护无效的Page_Load（对象发件人，EventArgs的）
{
    。字符串testCustNum = Page.Request.QueryString [custnum]的ToString（）;

    RhsCustomerRepository rcrep =新RhsCustomerRepository（）;
    RhsCustomer RC = rcrep.GetCustomer（testCustNum）;
    名单＆LT; RhsTruck＆GT;卡车= rcrep.GetEquipmentOwned（RC）;

    //我要显示的列表到一个GridView W /自动生成列
    GridViewTrucks.DataSource =卡车;
    GridViewTrucks.DataBind（）;
}
 

解决方案

现在的问题是，你正在使用<一个href="http://msdn.microsoft.com/en-us/library/system.linq.enumerable.singleordefault.aspx"><$c$c>SingleOrDefault.当集合正好包含0或1元这个方法才能成功。我相信你正在寻找<一href="http://msdn.microsoft.com/en-us/library/system.linq.enumerable.firstordefault.aspx"><$c$c>FirstOrDefault这将不管有多少元素集合中取得成功。

I'm having some issues with grabbing a list of type "RhsTruck" through Linq and getting them to display.

RhsTruck just has properites Make, Model, Serial etc... RhsCustomer has properties CustomerName, CustomerAddress, etc...

I keep getting the error "Sequence contains more than one element". Any ideas? Am I approaching this the wrong way?

public RhsCustomer GetCustomer(string customerNumber)
{
    using (RhsEbsDataContext context = new RhsEbsDataContext() )
    {
        RhsCustomer rc = (from x in context.custmasts
                          where x.kcustnum == customerNumber
                          select new RhsCustomer()
                        {
                            CustomerName = x.custname,
                            CustomerAddress = x.custadd + ", " + x.custcity
                            CustomerPhone = x.custphone,
                            CustomerFax = x.custfax
                        }).SingleOrDefault();
        return rc;
    }
}

public List<RhsTruck> GetEquipmentOwned(RhsCustomer cust)
{
    using (RhsEbsDataContext context = new RhsEbsDataContext())
    {
        var trucks = (from m in context.mkpops
                      join c in context.custmasts
                        on m.kcustnum equals c.kcustnum
                      where m.kcustnum == cust.CustomerNumber
                      select new RhsTruck
                    {
                        Make = m.kmfg,
                        Model = m.kmodel,
                        Serial = m.kserialnum,
                        EquipID = m.kserialno1,
                        IsRental = false
                    }).ToList();
        return trucks;
    }
}

protected void Page_Load(object sender, EventArgs e)
{
    string testCustNum = Page.Request.QueryString["custnum"].ToString();

    RhsCustomerRepository rcrep = new RhsCustomerRepository();
    RhsCustomer rc = rcrep.GetCustomer(testCustNum);
    List<RhsTruck> trucks = rcrep.GetEquipmentOwned(rc);

    // I want to display the List into a Gridview w/auto-generated columns
    GridViewTrucks.DataSource = trucks;
    GridViewTrucks.DataBind();   
}

解决方案

The problem is that you are using SingleOrDefault. This method will only succeed when the collections contains exactly 0 or 1 element. I believe you are looking for FirstOrDefault which will succeed no matter how many elements are in the collection.

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