从类返回的值将恢复为 null

本文关键字：恢复 null 返回 | 更新日期: 2023-09-27 18:22:08

我创建了一个新的承包商对象"gc"，它调用方法GetConcontracter((来返回所有属性。它返回的结果是正确的，但是"gc"对象显示所有"NULL"。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;
        }
    }
}

。.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; }
}

从类返回的值将恢复为 null

当你不把它分配给某物时，你会失去gc的值。

试试这个：

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

您正在创建仅用于调用 GetContractor 方法的对象的一个空实例。GetContractor 方法创建另一个包含数据的实例，该实例被返回，但您只需丢弃该实例，并期望数据在从未填充的第一个实例中可用。

将 GetContractor 方法设为静态，以便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;
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