ICollection的表达式<T> .Any(Func <T,bool>)

Question

我们假设我有以下模型:

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

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

我想为此建立一个Expression:

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,给出了以下错误:

Static method requires null instance, non-static method requires non-null instance. Parameter name: instance

当我刚才.GetMethods(BindingFlags.Static)没有得到任何Any()-Method不幸.

我该如何工作？

Answer 1

Any并且Where是扩展方法Enumerable,因此是static定义.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")
                                     )
                )