实体框架（QueryBuilder） - where子句“它”的前缀

Question

我最近遇到下面的实体框架语法。注意where子句 -

.Where("it.LastName = @ln AND it.FirstName = @fn") 

it.是做什么用的？而为什么it而不是Contacts.LastName？任何详细信息都会有帮助。提前致谢。

string firstName = @"Frances"; 
string lastName = @"Adams"; 

using (AdventureWorksEntities context = 
    new AdventureWorksEntities()) 
{ 
    // Get the contacts with the specified name. 
    ObjectQuery<Contact> contactQuery = context.Contacts 
     .Where("it.LastName = @ln AND it.FirstName = @fn", 
     new ObjectParameter("ln", lastName), 
     new ObjectParameter("fn", firstName)); 

    // Iterate through the collection of Contact items. 
    foreach (Contact result in contactQuery) 
     Console.WriteLine("Last Name: {0}; First Name: {1}", 
     result.LastName, result.FirstName); 
} 

Answer 1

基于this article，“它”指的ObjectQuery作为默认名称为参考参数。通过使用的ObjectQuery的Name属性，你实际上可以改变它，这样在你的where子句也可以作为任何名字，你希望它是被引用：

ObjectQuery<Contact> contactQuery; 
contactQuery.Name = "contact"; 
contactQuery = context.Contacts 
    .Where("contact.LastName = @ln AND contact.FirstName = @fn", 
    new ObjectParameter("ln", lastName), 
    new ObjectParameter("fn", firstName)); 

也许不完全像上面显示，但它给出了总体思路。