Question

我创建了一个新的Contractor对象＆＃34; gc＆＃34;调用方法GetContractor（）来返回所有属性。它返回的结果是正确的，但＆＃34; gc＆＃34;对象显示全部＆＃34; NULL＆＃34;。我假设我在aspx.cs页面中做错了什么？

aspx.cs

protected void fvWasteCollected_ItemCommand(object sender, FormViewCommandEventArgs e)
    {
    if (e.CommandName.Equals("Insert")){
       ValidationSummaryWasteDetail.ValidationGroup = "WasteReceivedDetail";
       if (IsValid) {
           odsMRWWasteCollectedDetail.InsertParameters["WasteTypeId"].DefaultValue = ddlWasteCollectedType.SelectedValue;
           odsMRWWasteCollectedDetail.InsertParameters["DisposalMethodId"].DefaultValue = ddl_disposalMethod.SelectedValue;          
           Contractor gc = new Contractor();
           gc.GetContractor(2);
           var contractorName = gc.MRWContractorName;
        }
    }
}

的.cs

public class Contractor
{
  public Contractor GetContractor(int MRWContractorId)
    {
        using (DataAccessLINQDataContext db = new DataAccessLINQDataContext())
        {
            var result = db.MRWContractors.Where(c => c.MRWContractorId == MRWContractorId).Select(c => new Contractor
                {
                    MRWContractorId = c.MRWContractorId,
                    MRWContractorName = c.MRWContractorName,
                    MRWContractorAddress = c.MRWContractorAddress,
                    MRWContractorCity = c.MRWContractorCity,
                    MRWContractorStateCode = c.MRWContractorStateCode,
                    MRWContractorZipCode = c.MRWContractorZipCode,
                    MRWContractorPhone = c.MRWContractorPhone,
                    MRWContractorFax = c.MRWContractorFax,
                    MRWContractorEmail = c.MRWContractorEmail
                }).SingleOrDefault();

            return result;
        }
    }

    public int MRWContractorId { get; set; }
    public string MRWContractorName { get; set; }
    public string MRWContractorAddress { get; set; }
    public string MRWContractorCity { get; set; }
    public string MRWContractorStateCode { get; set; }
    public int? MRWContractorZipCode { get; set; }
    public string MRWContractorPhone { get; set; }
    public string MRWContractorFax { get; set; }
    public string MRWContractorEmail { get; set; }
}

Answer 1

如果不将其分配给某些内容，则会失去gc的值。

请改为尝试：

var contractor = gc.GetContractor(2);
var contractorName = contractor.MRWContractorName;

Answer 2

您正在创建一个仅用于调用GetContractor方法的对象的空实例。 GetContractor方法创建另一个包含数据的实例，该实例将被返回，但您只需抛弃该实例，并期望数据在第一个从未填充过的实例中可用。

将GetContractor方法设为静态，这样您就不需要实例来调用它：

public static Contractor GetContractor(int MRWContractorId)

现在，您可以调用该方法来获取包含数据的实例，而无需先创建空实例：

Contractor gc = Contractor.GetContractor(2);
string contractorName = gc.MRWContractorName;

从类返回的值恢复为null

2 个答案: