vb.net - 在 VB.net 中使用 Linq 编写连接查询

Question

我试图在 vb 中将 SQL 查询转换为 linq 查询。但是我在语法正确方面遇到了一些麻烦。

原始查询

SELECT b.* 
FROM History_Table_B b 
INNER JOIN Employee e ON b.EmployeeId = e.EmployeeId 
INNER JOIN Company c ON e.CompanyId = c.CompanyId 
WHERE e.AncillaryId = @AncillaryPersonId 
AND c.AncillaryId = @AncillaryCompanyId
AND (b.EndDate is null OR b.EndDate >= convert(date, GetDate()))

我的林克

Dim result = From b In context.H_Table_B
             Join employee In context.Employees
             On b.EmployeeId Equals (employee.EmployeeId)
             Join company In context.Companies
             On employee.CompanyId Equals (company.CompanyId) 
             Where employee.AncillaryId Equals(iPerId) 
             And company.AncillaryId Equals (iCompanyId) 
             And ((b.EndDate Is Nothing) Or (b.EndDate Equals(DateTime.Today)))

Answer 1

在 where 条件下，您不能像 Join LINQ 查询那样使用等于(运算符)。这里的 Equals 是对象类的一个方法，因此您可以使用 '.' 访问。例如employee.AncillaryId.Equals(iCompanyId)
还有一件事在新行VB.net的Where条件需要'_'。

例如

From b In context.H_Table_B
         Join employee In context.Employees
         On b.EmployeeId Equals (employee.EmployeeId)
         Join company In context.Companies
         On employee.CompanyId Equals (company.CompanyId) 
         Where employee.AncillaryId.Equals(iPerId) _ 
         And company.AncillaryId.Equals(iCompanyId) _
         And ((b.EndDate Is Nothing) Or (b.EndDate.Equals(DateTime.Today)))