How to delete all the specified contents from an object in a list in C#

Question

I have a list that looks like the following:

STUDENT: John, TEST ONE: A, TEST TWO: A, TEST THREE: D
STUDENT: Greg, TEST ONE: F, TEST TWO: B, TEST THREE: D

How can I delete the data for a specific student once the user inputs the name? I've tried doing the following but it doesn't work:

List<object> list = new List<object>(); // contains the list of students that
                                       //  were appended

Then, inside of a method here is some of the code that I wrote:

Console.Write("Enter the name of the student you want to remove: ");
string removedStudent = Console.ReadLine();
list.RemoveAll(s => s == removedStudent);

When the code runs and I input Greg as the name of the student I want to remove, nothing happens. I print the list and Greg is still in the list. So, instead of printing like this:

STUDENT: John, TEST ONE: A, TEST TWO: A, TEST THREE: D

It still prints like:

STUDENT: John, TEST ONE: A, TEST TWO: A, TEST THREE: D
STUDENT: Greg, TEST ONE: F, TEST TWO: B, TEST THREE: D

Is there a way I can delete the entire row just by specifying the name of the student?

Edit:

Here is the part where I ask the user to input the student information:

class StudentsIO
{
    public object getInput()
    {
        Console.Write("Enter student name: ");
        string studentName = Console.ReadLine();
        Console.Write("Enter test 1 score: ");
        string test1 = Console.ReadLine();
        Console.Write("Enter test 2: ");
        string test2 = Console.ReadLine();
        Console.Write("Enter test 3: ");
        string test3 = Console.ReadLine()
        Students students = new Students(studentName,test1,test2,test3);
        return students;
    }
}

Here's where I add students to the list:

StudentIO newStudent = new StudentIO();
object studentList = newStudent.getInput();
list.Add(studentList);

Linq should be `list.RemoveAll(s => s.STUDENT == removedStudent);` — juanvan, Dec 03 '15 at 03:13
@RonBeyer I originally did have it as Student instead of object but my code threw a bunch of error, specifically when I tried appending a new student. It started working when I changed it to object. — jo13, Dec 03 '15 at 03:15
If you were getting errors when appending to `List` that is another issue that you need to address. It is seldom, if ever, a good idea to use `List — T Burnside, Dec 03 '15 at 03:27
@joanne72205 Can you show us what you are doing when you are adding students? Are you, perchance, typing `list.Add("Greg")`? I'm wondering if you are inadvertently creating a list of strings _as objects_ instead of adding Student objects to your list. — Andrew Palmer, Dec 03 '15 at 04:03
@AndyPalmer I added an edit where I copied some of the code that I used to ask the user various questions and then where I save it to the list. — jo13, Dec 03 '15 at 04:22
The signature of your method should be `public Students getInput()` and your assignment should be `Students studentLIst = newStudent.getInput()` or simply `var studentList = newStudent.getInput()`. Then you could have a `List`. — T Burnside, Dec 03 '15 at 04:46
@TBurnside Your suggestion completely fixed all my problems! It makes sense now that I'm looking at the code with your edit and I don't know why I didn't implement it in the first place. — jo13, Dec 03 '15 at 05:10

score 1 · Accepted Answer · answered Dec 03 '15 at 03:19

First, as Ron Beyer implies in his comment, you should be using something more specific than List<object>. I'm not sure what data type your students are, but let's say they are a class Student, with a STUDENT property that specifies the name. You would then have List<Student>.

Since the list contains objects (not Students), 1ist.removeAll(s => s == removedStudent) is using the == operator defined on object, which does object comparison. The string you entered is NOT the same object as the Student in the list. If you have a List<Student>, you would then use:

list.removeAll(s => s.STUDENT == removedStudent);

to remove the student from the list.

score 0 · Answer 2 · edited May 23 '17 at 11:44

0

I can't tell what your object looks like from your question, but have you tried something like this?

list.RemoveAll(s => s.STUDENT == removedStudent);

Answered here as well

edited May 23 '17 at 11:44

Community

1
1

answered Dec 03 '15 at 03:15

BSSchwarzkopf

352
2
11

score 0 · Answer 3 · answered Dec 03 '15 at 05:49

0

I'd suggest:

students.RemoveAll(s => string.Compare(s.Name, studentNameToRemove, true) == 0);

answered Dec 03 '15 at 05:49

Tathagat Verma

549
7
12

How to delete all the specified contents from an object in a list in C#

3 Answers3