c# - LINQ to Sharepoint InsertOnSubmit 问题

Question

例如，我有一个名为 Product 的列表，它有 3 列，ProductName(即标题)、ProductPrice 和 ProductType。

• ProductName 是一个字符串
• ProductPrice 是一种货币( double )
• ProductType 是对 ProductTypes 列表的查找

通常，如果它不包含查找列，这对我来说很容易，但我不知道如何在插入时处理查找列。

我试过这个，但它返回错误 Specified cast is not valid.

这是当前代码

EntityList<ProductTypeItem> ProductTypes = dc.GetList<ProductTypeItem>("ProductType");

ProductItem newProduct = new ProductItem();

newProduct.Title = txtProductName.Text;
newProduct.ProductPrice = double.Parse(txtProductPrice.Text); 
newProduct.ProductType = (from a in ProductTypes where a.Title == ddProductType.SelectedItem.Text select a).FirstOrDefault();

dc.Product.InsertOnSubmit(newProduct);
dc.SubmitChanges();   

我将如何处理 newProduct.ProductType，因为这里是错误发生的地方。

请注意 ddProductType 数据源是 ProductType List 并在其 DataTextField 和 DataValueField 中使用 Title/p>

Answer 1

This 可能会帮助您。第一个示例说明插入应如何与现有数据的链接一起使用。此示例代码应为您提供足够的提示来帮助您解决问题:

AdventureWorksDataContext db = new AdventureWorksDataContext();

// LINQ query to get StateProvince
StateProvince state = (from states in db.StateProvinces
                       where states.CountryRegionCode == "AU" && states.StateProvinceCode == "NSW"
                       select states).FirstOrDefault();
// LINQ function to get AddressType
AddressType addrType = db.AddressTypes.FirstOrDefault(s => s.Name == "Home");

Customer newCustomer = new Customer()
{
    ModifiedDate= DateTime.Now,
    AccountNumber= "AW12354", 
    CustomerType='I',
    rowguid= Guid.NewGuid(),
    TerritoryID= state.TerritoryID    // Relate record by Keys
};
Contact newContact = new Contact()
{
    Title = "Mr",
    FirstName = "New",
    LastName = "Contact",
    EmailAddress = "newContact@company.com",
    Phone = "(12) 3456789", 
    PasswordHash= "xxx",
    PasswordSalt= "xxx",
    rowguid = Guid.NewGuid(),
    ModifiedDate = DateTime.Now
};
Individual newInd = new Individual()
{
    Contact= newContact,    // Relate records by objects (we dont actually know the Keys for the new records yet)
    Customer= newCustomer,
    ModifiedDate= DateTime.Now
};
Address newAddress = new Address()
{
    AddressLine1= "12 First St",
    City= "Sydney",
    PostalCode= "2000", 
    ModifiedDate=DateTime.Now,
    StateProvince= state,
    rowguid = Guid.NewGuid()
};

// Link our customer with their address via a new CustomerAddress record
newCustomer.CustomerAddresses.Add(new CustomerAddress() { Address = newAddress, Customer = newCustomer, AddressType = addrType, ModifiedDate = DateTime.Now, rowguid = Guid.NewGuid() });

// Save changes to the database
db.SubmitChanges();