得到“不支持计数”的异常

Question

我正在开发一个Windows Phone 7应用程序，我想自动增加使用代码优先技术创建的数据库值。 我尝试了下面的逻辑来完成这件事，但其造成的异常“计数法不支持”

var c = new AccountEntryModel(); 
Expense exp = new Expense(); 
if (c.Expenses.Count() == 0) 
exp.ExpenseId = 1; 
else 
exp.ExpenseId = c.Expenses.Max<Expense>(b => b.ExpenseId) + 1; 
ExpenseIdTextBox.Text = exp.ExpenseId.ToString(); 

Answer 1

我想你的代码，并在Windows手机工作得很好7.1

这里是我的尝试：

var c = new AccountEntryModel(); 
Expense exp = new Expense(); 
if (c.Expenses.Count() == 0) 
    exp.ExpenseId = 1; 
else 
    exp.ExpenseId = c.Expenses.Max<Expense>(b => b.ExpenseId) + 1; 

这里是我在我的假设建立在您的代码上面的类：

public class Expense 
{ 
    public int ExpenseId { get; set;} 
} 

public class AccountEntryModel 
{ 
    public AccountEntryModel() 
    { 
     Expenses = new List<Expense>(); 

     for (int i = 1; i < 10; i++) 
     { 
      Expenses.Add(new Expense { ExpenseId = i }); 
     } 

    } 
    public List<Expense> Expenses { get; set;} 
}