Develop Reference

Set Object null if all its properties are null in C#

I want to write a function which it turns every properies and child properties of an object. And if all properties of one property are null, then I will set that property as null. I will explain with one example.
For example, if both TeacherName and TeacherSurname are null then I want to set Teacher to null. Then, if ExamMark and ExamName and Teacher are null, then Exam will be null.
You can see json version of like my question from this link Json Version
public class Student
{
public string Name { get; set; }
public string Surname { get; set; }
public Address Address { get; set; }
public Exam Exam { get; set; }
}
public class Exam
{
public string ExamMark { get; set; }
public string ExamName { get; set; }
public Teacher Teacher { get; set; }
}
public class Teacher
{
public string TeacherName { get; set; }
public string TeacherSurname { get; set; }
}
public class Address
{
public string Country { get; set; }
public string City { get; set; }
}
I wrote this method. But this doing only first step. But I need recursive for child class. How can I convert this method to recursive?
public static object ConvertToNull(object obj)
{
Type objType = obj.GetType();
PropertyInfo[] properties = objType.GetProperties();
var mainClassProperties = properties.Where(p => p.PropertyType.Assembly == objType.Assembly);
foreach (var mainClassProperty in mainClassProperties)
{
object propValue = mainClassProperty.GetValue(obj, null);
var classAllProperties = propValue.GetType().GetProperties();
if (propValue.GetType().GetProperties().All(propertyInfo => propertyInfo.GetValue(propValue) == null))
{
mainClassProperty.SetValue(obj, null);
}
}
return obj;
}

What you're asking for is actually an anti-pattern. What this does is it propagates the requirement for tons of null checks in your code. Not only do you have to check if all properties are null, you also have to check if your object is null when you want to use it. Also reflection is very slow and if you're doing this often, you'll bog down your application.
You should look into the Null Object Pattern. It basically does what you want it to, and you remove all those pesky null checks:
public class Student
{
public string Name { get; set; }
public string Surname { get; set; }
public Address Address { get; set; }
public Exam Exam { get; set; }
public static Student NullStudent { get; } = new Student
{
Name = null,
Surname = null,
Address = Address.NullAddress,
Exam = Exam.NullExam,
}
}
You can do this for each object in your code that acts this way (you can see that I did it on your nested Address and Exam types as well) and then instead of doing this:
if (Student.EverythingIsNull) { Student = null }
if (Student is null) { //do null stuff }
You can do this:
if (item == Student.NullStudent) { //do null stuff }
This leads to clearer code, your intent stands out more, and you can specifically define in each object what constitutes as null.

using Generics and Reflection.
public T ConvertToNull<T>(T model) where T : class
{
if (model == null) return null;
Type type = model.GetType();
PropertyInfo[] properties = type.GetProperties();
var valueTypes = properties.Where(p => p.PropertyType.Assembly != type.Assembly);
var nonValueTypes = properties.Where(p => p.PropertyType.Assembly == type.Assembly);
foreach (var nonValueType in nonValueTypes)
nonValueType.SetValue(model, ConvertToNull(nonValueType.GetValue(model)));
if (valueTypes.All(z => z.GetValue(model) == null) && nonValueTypes.All(z => z.GetValue(model) == null))
return null;
else
return model;
}
Here you can call it
List<Student> students = new List<Student>();
Student student = new Student() { Name = "StudentName", Surname = "StudentSurname", Address = new Address() { City = "City", Country = "Country" }, Exam = new Exam() { ExamMark = "ExamMark", ExamName = "ExamName", Teacher = new Teacher() { TeacherName = "TeacherName", TeacherSurname = "TeacherSurname" } } };
Student student2 = new Student() { Name = "StudentName", Surname = "StudentSurname", Address = new Address(), Exam = new Exam() { ExamMark = "ExamMark", ExamName = "ExamName", Teacher = new Teacher() } };
students.Add(student);
students.Add(student2);
List<Student> results = new List<Student>();
foreach (var item in students)
{
var result = ConvertToNull(item);
results.Add(result);
}

Have a look at this The GetValueOrNull should work and do what you need, not tested with all possible use cases but it oculd be tweaked a little if doesn't work in all cases
public static bool IsSimpleType(Type type)
{
return
type.IsPrimitive ||
new Type[] {
typeof(Enum),
typeof(String),
typeof(Decimal),
typeof(DateTime),
typeof(DateTimeOffset),
typeof(TimeSpan),
typeof(Guid)
}.Contains(type) ||
Convert.GetTypeCode(type) != TypeCode.Object ||
(type.IsGenericType && type.GetGenericTypeDefinition() == typeof(Nullable<>) && IsSimpleType(type.GetGenericArguments()[0]))
;
}
public object GetValueOrNull(object obj)
{
if (obj == null) return null;
Type objType = obj.GetType();
PropertyInfo[] properties = objType.GetProperties();
var simpleTypes = properties.Where(t => IsSimpleType(t.PropertyType));
var nonValueTypes = properties.Where(p => !simpleTypes.Contains(p));
foreach (var child in nonValueTypes)
{
child.SetValue(obj, GetValueOrNull(child.GetValue(obj)));
}
return simpleTypes.All(z => z.GetValue(obj) == null) && nonValueTypes.All(z => z.GetValue(obj) == null) ? null : obj;
}
call it as follows
var student = new Student { Address = new Address { }, Exam = new Exam { Teacher = new Teacher() } };
var test = GetValueOrNull(student);
hope it helps :)

Using Dictionary Parameters as Optional Arguments when Calling Method

I'm presently trying to use a dictionary values to name optional parameters when invoking a method. I'm not sure this is possible with c# but I do something similar with queries using dynamic SQL.
string[] dobArrayKey = {"dob: "};
string[] dobArrayValue = {txtDob.Text};
string[] ptntNumArrayKey = { "PatientID: " };
string[] ptntNumArrayValue = { txtOfficeMR.Text};
string[] nameArrayKey = { "FirstName: ", "LastName: " };
string[] nameArrayValue = { txtFirstname.Text, txtLastname.Text };
List<List<string>> searchResults = new List<List<string>>();
Dictionary<string[], string[]> searchCriteria = new Dictionary<string[], string[]>
{
{dobArrayKey,dobArrayValue}
,{ptntNumArrayKey,ptntNumArrayValue}
,{nameArrayKey,nameArrayValue}
};
foreach (var item in searchCriteria)
{
if (item.Value[0] != "" && item.Value[0] != null)
{
searchResults.Add(new List<string>());
for (int x = 0; x <= item.Key.Count(); x++)
{
string strJSON = doPatientSearch(Convert.ToInt32(au.UserID)
, Convert.ToInt32(Session["PracticeID"]), au.SessionID, item.Key[x].ToString() : item.Value[x].ToString() );
PatientSearchResponse ptLi = JsonConvert.DeserializeObject<PatientSearchResponse>(json2);
foreach (PatientList3 patient in ptLi.PatientList)
{
searchResults[x].Add(patient.PatientNumber);
}
}
}
}
public static string doPatientSearch(int UserID, int PracticeID, string SessionID, string PatientID = null,
,string first = null, string last = null, string dob = null, string social = null)
{
//search
}
My colleague suggested I change the method itself by removing all of the optional parameters and instead passing through a dictionary that contains all of the parameters and handling them inside the method.
I think that would work, but for curiosities sake I wanted to get some feedback and find out whether or not something like I'm attempting to do in the above code is possible.
If it is impossible but there is another way of achieving the desired outcome I'd love to see your suggestions.
Thank you in advance.

Pass an expression
Since the criteria are used post-hoc (i.e. by filtering a complete resultset), you can use LINQ to filter the results. For maximum flexibility, the caller can pass in an Expression to be used as a callback on each item to determine if it should be included.
To get a filtered resultset:
public IEnumerable<Patient> FindPatients(Func<Patient,bool> criteria)
{
return sourceData
.Where (criteria);
}
To return a single result:
public Patient FindPatient(Func<Patient,bool> criteria)
{
return sourceData
.Single(criteria);
}
The criteria expression is just a function that accepts a patient and returns a Boolean. The caller can write this any way desired, or insert it as a lambda expression.
var results = patients.FindPatients( p => p.LastName == "Doe" );
Or
var results = patients.FindPatients
(
p =>
p.LastName.Contains("Doe") &&
p.PracticeID == 12
);
Or
var singleResult = patients.FindPatient( p => p.UserID == 1);
As you can see, the caller can provide literally any criteria desired, and has the benefit of type safety and early binding. This is far superior to using a Dictionary which has neither.
Full example code:
class Patient
{
public int UserID { get; set; }
public int PracticeID { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public DateTime DOB { get; set; }
public string Social { get; set; }
public override string ToString()
{
return string.Format("{0} {1} {2}", UserID, FirstName, LastName);
}
}
class PatientRepository
{
static private readonly List<Patient> sourceData = new List<Patient>
{
new Patient
{
UserID = 1, PracticeID = 10, FirstName = "John", LastName = "Doe", DOB = DateTime.Parse("1/2/1968"), Social="123456789"
},
new Patient
{
UserID = 2, PracticeID = 10, FirstName = "Jane", LastName = "Doe", DOB = DateTime.Parse("1/2/1958"), Social="123456790"
},
new Patient
{
UserID = 3, PracticeID = 10, FirstName = "John", LastName = "Carson", DOB = DateTime.Parse("4/1/1938"), Social="123456791"
}
};
public IEnumerable<Patient> FindPatients(Func<Patient,bool> criteria)
{
return sourceData
.Where (criteria);
}
public Patient FindPatient(Func<Patient,bool> criteria)
{
return sourceData
.Single(criteria);
}
}
public class Program
{
public static void Main()
{
//Get a reference to the data store
var patients = new PatientRepository();
Console.WriteLine("Multiple record search");
var results = patients.FindPatients
(
p => p.LastName == "Doe"
);
foreach (var p in results)
{
Console.WriteLine(p);
}
Console.WriteLine("Single record search");
var singleResult = patients.FindPatient
(
p => p.UserID == 1
);
Console.WriteLine(singleResult);
}
}
Output:
Multiple record search
1 John Doe
2 Jane Doe
Single record search
1 John Doe
See the working code on DotNetFiddle

Comparing dataset with array of data asp net

I have this page of operators that has two tables with data from database, one table with existing operators and one table with existing users. If a user is already an operator, I want that row to be hidden in the table. Here is my code:
C#:
var userDetailsList = new List<ContactPartial>();
TellusAPI.TellusUserDetails userDetails;
var operators = _administrationSystem.GetOperatorsInformation(userId); //DataSet
var getUser = webSearch.DoSearchForNameAndNumber(userId, txtSearchForOperator.Text, false, "", "", false, false, out userDetails); //Array
if (getUser == null)
{
userDetailsList.Add(new ContactPartial(userDetails));
rptAdd.DataSource = null;
}
else
{
var query = getUser.Where(y => y.ID == (long)operators.Tables[0].Rows[0]["ID"]).Select(x => x.ID);
var result = from o in operators.Tables[0].AsEnumerable()
where o.Field<int>("ID") == Convert.ToInt64(query)
select o;
rptAdd.DataSource = result;
}
Class:
/// <summary>
/// Class for converting.
/// </summary>
public class ContactPartial
{
public long Id { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
public string CompanyName { get; set; }
public string Email { get; set; }
public ContactPartial(TellusUserDetails tud)
{
if (tud == null)
{
return;
}
Id = tud.UserID;
FirstName = tud.FirstName;
LastName = tud.LastName;
CompanyName = tud.Organisation.Description;
Email = tud.Email;
}
public ContactPartial(TellusSearchUserInfo tsi)
{
if (tsi == null)
{
return;
}
Id = tsi.ID;
FirstName = tsi.FirstName;
LastName = tsi.LastName;
CompanyName = tsi.CompanyName;
Email = tsi.Email;
}
}
So I now compare these two and filter the rows with ID, but it still reads all rows. Why?

How can I create set contain id record in first set equal id record in second set?

In database I have two tables:
public partial class PersonOne
{
public int id { get; set; }
public string name { get; set; }
public string surname { get; set; }
}
public partial class PersonTwo
{
public int id { get; set; }
public string firstname { get; set; }
public string lastname { get; set; }
}
I would like to fill my set:
public class PersonOnePersonTwo
{
public int PersonOneId { get; set; }
public int PersonTwoId { get; set; }
}
where PersonOne.name == PersonTwo.firstname && PersonOne.surname == PersonTwo.lastname but I have no idea how I can do that - because below code isn't efficient and is so slow:
List<PersonOne> personOneList = new List<PersonOne>();
List<PersonTwo> personTwoList = new List<PersonTwo>();
List<PersonOnePersonTwo> personOnePersonTwoList = new List<PersonOnePersonTwo>();
foreach (PersonOne personOne in personOneList)
{
foreach(PersonTwo personTwo in personTwoList.Where(x => x.firstname == personOne.name && x.lastname == personOne.surname).ToList())
{
personOnePersonTwoList.Add(new PersonOnePersonTwo
{
PersonOneId = personOne.id,
PersonTwoId = personTwo.id
});
}
};

Try this:
var result = personOneList.Join
(
personTwoList,
person1 => new { Key1 = person1.Name, Key2 = person1.Surname },
person2 => new { Key1 = person2.FirstName, Key2 = person2.LastName },
(person1, person2) => new PersonOnePersonTwo { PersonOneId = person1.Id, PersonTwoId = person2.Id }
).ToList();

I would go with:
var personOnePersonTwoList = new List<PersonOnePersonTwo>();
foreach (var personOne in personOneList)
{
personOnePersonTwoList = personTwoList.Where(x => x.firstname.Equals(personOne.name, StringComparison.OrdinalIgnoreCase) &&
x.lastname.Equals(personOne.surname, StringComparison.OrdinalIgnoreCase))
.Select(x => new PersonOnePersonTwo {PersonOneId = personOne.id, PersonTwoId = x.id}).ToList();
};
As a side note: it's more convinient to use Equals when comparing strings.

Uppercase a List of object with LINQ

I have the code below. I'd like to convert all items in this list to uppercase.
Is there a way to do this in Linq ?
public class Person
{
public string FirstName { get; set; }
public string LastName { get; set; }
public int Age { get; set; }
}
public class MyClass
{
List<Person> myList = new List<Person>{
new Person { FirstName = "Aaa", LastName = "BBB", Age = 2 },
new Person{ FirstName = "Deé", LastName = "ève", Age = 3 }
};
}
Update
I don't want to loop or go field by field. Is there a way by reflection to uppercase the value for each property?

Why would you like to use LINQ?
Use List<T>.ForEach:
myList.ForEach(z =>
{
z.FirstName = z.FirstName.ToUpper();
z.LastName = z.LastName.ToUpper();
});
EDIT: no idea why you want to do this by reflection (I wouldn't do this personally...), but here's some code that'll uppercase all properties that return a string. Do note that it's far from being perfect, but it's a base for you in case you really want to use reflection...:
public class Person
{
public string FirstName { get; set; }
public string LastName { get; set; }
public int Age { get; set; }
}
public static class MyHelper
{
public static void UppercaseClassFields<T>(T theInstance)
{
if (theInstance == null)
{
throw new ArgumentNullException();
}
foreach (var property in theInstance.GetType().GetProperties(BindingFlags.Public | BindingFlags.Instance))
{
var theValue = property.GetValue(theInstance, null);
if (theValue is string)
{
property.SetValue(theInstance, ((string)theValue).ToUpper(), null);
}
}
}
public static void UppercaseClassFields<T>(IEnumerable<T> theInstance)
{
if (theInstance == null)
{
throw new ArgumentNullException();
}
foreach (var theItem in theInstance)
{
UppercaseClassFields(theItem);
}
}
}
public class Program
{
private static void Main(string[] args)
{
List<Person> myList = new List<Person>{
new Person { FirstName = "Aaa", LastName = "BBB", Age = 2 },
new Person{ FirstName = "Deé", LastName = "ève", Age = 3 }
};
MyHelper.UppercaseClassFields<Person>(myList);
Console.ReadLine();
}
}

LINQ does not provide any facilities to update underlying data. Using LINQ, you can create a new list from an existing one:
// I would say this is overkill since creates a new object instances and
// does ToList()
var updatedItems = myList.Select(p => new Person
{
FirstName = p.FirstName.ToUpper(),
LastName = p.LastName.ToUpper(),
Age = p.Age
})
.ToList();
If using LINQ is not principal, I would suggest using a foreach loop.
UPDATE:
Why you need such solution? Only one way of doing this in generic manner - reflection.

the Easiest approach will be to use ConvertAll:
myList = myList.ConvertAll(d => d.ToUpper());
Not too much different than ForEach loops the original list whereas ConvertAll creates a new one which you need to reassign.
var people = new List<Person> {
new Person { FirstName = "Aaa", LastName = "BBB", Age = 2 },
new Person{ FirstName = "Deé", LastName = "ève", Age = 3 }
};
people = people.ConvertAll(m => new Person
{
FirstName = m.FirstName?.ToUpper(),
LastName = m.LastName?.ToUpper(),
Age = m.Age
});
to answer your update
I don't want to loop or go field by field. Is there a way by
reflection to uppercase the value for each property?
if you don't want to loop or go field by field.
you could use property on the class to give you the Uppercase like so
public class Person
{
public string FirstName { get; set; }
public string LastName { get; set; }
public int Age { get; set; }
public string FirstNameUpperCase => FirstName.ToUpper();
public string LastNameUpperCase => LastName.ToUpper();
}
or you could use back field like so
public class Person
{
private string _firstName;
public string FirstName {
get => _firstName.ToUpper();
set => _firstName = value;
}
private string _lastName;
public string LastName {
get => _lastName.ToUpper();
set => _lastName = value;
}
public int Age { get; set; }
}

You can only really use linq to provide a list of new objects
var upperList = myList.Select(p=> new Person {
FirstName = (p.FirstName == null) ? null : p.FirstName.ToUpper(),
LastName = (p.LastName == null) ? null : p.LastName.ToUpper(),
Age = p.Age
}).ToList();

p.lastname.ToString().ToUpper().Contains(TextString)