LINQ to SQL将对象作为参数传递

Question

To select something with LINQ to SQL this is what we normally do:

        DataClassesDataContext context = new DataClassesDataContext();
        var value = from employee in context.Employees
                               orderby employee.Salary descending
                               select employee;

What if i have like 30 table and i want to write this once in a method and only pass parameters to the function to call some table like this:

    public void select_function(Parameter1,Parameter2)
{
    DataClassesDataContext context = new DataClassesDataContext();
    var value = from Parameter1 in context.Parameter2
                               orderby Parameter1.Salary descending
                               select Parameter1;
}

is that even possible ?

Answer 1

You can use GetTable<T> generic method of LINQ to SQL Data Context object. And pass an expression for sorting:

public void select_function<T, TProperty>(Expression<Func<T, TProperty>> orderBy)
    where T : class
{
    DataClassesDataContext context = new DataClassesDataContext();
    var value = context.GetTable<T>().OrderByDescending(orderBy);
}

Usage:

select_function((Employee e) => e.Salary)

Though you simply can do

var value = context.GetTable<Employee>().OrderByDescending(e => e.Salary);

without creating any methods