c# - ICollection.Any(Func) 的表达式

Question

假设我有以下模型:

public class Department
{
    public ICollection<Employee> Employees { get; set; }
}

public class Employee
{
    public string Name { get; set; }
}

我想为此构建一个表达式:

departments.Where(x => x.Employees.Any(y => y.Name.Contains("foo")))

我有以下代码:

var departmentParameterExpression = Expression.Parameter(typeof(Department), "x");
PropertyExpression departmentListProperty = { x.Departments } // Value of the Expression shown in the debugger, actual code is some property helper to get the property by Name
var employeeParameterExpression = Expression.Parameter(typeof(Employee), "y");
PropertyExpression employeeNameProperty = { y.Name } // Same as departmenListProperty
var employeeNameContainsString = Expression.Call(employeeNameProperty, typeof(string).GetMethod("Contains"), Expression.Constant(token));
var compiledExpression = Expression.Lambda<Func<Employee, bool>>(employeeNameContainsString, employeeParameterExpression).Compile();

var anyMethod = typeof(Enumerable).GetMethods(BindingFlags.Static | BindingFlags.Public | BindingFlags.Instance).FirstOrDefault(x => x.Name == "Any" && x.GetParameters().Length == 2 &&  x.GetGenericArguments().Length == 1).MakeGenericMethod(typeof(Employee));

var containsEmployeeWithSearchString = Expression.Call(departmentListProperty, anyMethod, Expression.Constant(compiledExpression);

运行最后一行，出现以下错误:

静态方法需要空实例，非静态方法需要非空实例。参数名称:实例

不幸的是，当我只有 .GetMethods(BindingFlags.Static) 时，我没有得到任何 Any()-Method。

我如何使它工作？

Answer 1

Any 和 Where 是 Enumerable 的扩展方法，因此根据定义是 static。您尝试构建的实际 表达式将等效于:

Enumerable.Where(departments, 
                 x => Enumerable.Any(x.Employees,
                                     y => y.Name.Contains("foo")
                                     )
                )