How to re-validate model in C#?

Question

I have a list in model like below:

{
  "DepartmentId": 0,
  "Employees": [
    {
      "EmployeeId": 101,
      "EmployeeName": "Employee One",
      "DepartmentId": "1"
    },
    {
      "EmployeeId": 102,
      "EmployeeName": "Employee Two",
      "DepartmentId": "2"
    },
    {
      "EmployeeId": 0,
      "EmployeeName": "Employee Three",
      "DepartmentId": ""
    }
  ]
}

and because of one item in the list is not valid so ModelState.IsValid returns false. Now I have removed that item from the list like below:

{
  "DepartmentId": 0,
  "Employees": [
    {
      "EmployeeId": 101,
      "EmployeeName": "Employee One",
      "DepartmentId": "1"
    },
    {
      "EmployeeId": 102,
      "EmployeeName": "Employee Two",
      "DepartmentId": "2"
    }
  ]
}

Now, Please anyone tell me how can I re-validate model.

Below is the actual code is am using:

public void Settings(Companies companies)
{
    try
    {
        // This is the code that I am using to remove item from list.
        companies.Employees.Remove(companies.Employees.Find(x => x.IsActive == false && x.EmployeeId == 0));  

        // Now here I want to re-validate the model.

        if (ModelState.IsValid)
        {
            // To Do
        }
    }
    catch() {}
}