Solve task 1

Tasks/DT1/DT1.cs

@@ -17,9 +17,20 @@ namespace DT1 {
     }
 
     public class StudentClass {
-        public Func<Student, string, bool> studentSelector = /* TO BE DONE */ 
-        public GradeCalc gradeCalculator = /* TO BE DONE */
-        public Func<Student, bool> passedSelector = /* TO BE DONE */ 
+        public Func<Student, string, bool> studentSelector = (student, surname) =>
+        {
+            return string.Compare(student.LastName, surname, true) == 0;
+        };
+
+        public GradeCalc gradeCalculator = (grades) =>
+        {
+            return Math.Round(((grades.Average() / 100 * 5) + 1) * 2, MidpointRounding.AwayFromZero) / 2;
+        };
+
+        public Func<Student, bool> passedSelector = (student) =>
+        {
+            return student.Year == GradeLevel.FourthYear && student.Grade >= 4;
+        };
 
         #region data
         public List<Student> students = new List<Student> {
@@ -70,15 +81,16 @@ namespace DT1 {
         }
 
         public List<Student> SearchStudent(Func<Student, string, bool> select, String lastName) {
-            List<Student> result = new List<Student>();
+            List<Student> result = new() { };
             foreach (Student s in students) {
                 if (select(s, lastName)) result.Add(s);
             }
             return result;
         }
 
-        public IEnumerable<Student> QueryPassed(Func<Student,bool> passed) {
-            return /* TO BE DONE */ 
+        public IEnumerable<Student> QueryPassed(Func<Student,bool> passed)
+        {
+            return students.Where(passed);
         }
 
         static void show(String titel, List<Student> students) {
@@ -101,7 +113,10 @@ namespace DT1 {
         
     }
     public static class ListUtils {
-        public static IEnumerable<T> ... /* TO BE DONE */
+        public static IEnumerable<T> What<T>(this IList<T> list, Func<T, bool> selector)
+        {
+            return list.Where(selector);
+        }
     }
 
 }

Tasks/DT1/DT1.csproj

@@ -4,7 +4,7 @@
     <OutputType>Exe</OutputType>
     <TargetFramework>net8.0</TargetFramework>
     <ImplicitUsings>enable</ImplicitUsings>
-    <Nullable>enable</Nullable>
+    <Nullable>disable</Nullable>
   </PropertyGroup>
 
 </Project>