Member Avatar for ROTC89

ok so im trying to search list for a student by the last name and i keep getting a error as
Error 1 Cannot convert type 'string' to 'Project2.Person'
and i do not know how to fix it. any advice?

class StudentData
    {   private List<string> Page;
 
        public StudentData()
        {   Page = new List<string>();
        }

      

        public Person searchStudent(string Lname) //searches for a Person based on their last name
        {
            foreach(Person search in Page)
            {
                if (search.getLastName().ToLower() == Lname.ToLower())
                {
                    return search;
                }
            }
            r
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  • Latest Post Latest Post by apegram

Dani AI

Generated

The replies already point at the immediate symptom. To make the search reliable and maintainable, prefer working with typed Person instances and use a case-insensitive, null-safe comparison rather than ad-hoc string parsing each time. Below are two practical patterns you can apply depending on how often searches run and whether multiple people can share the same last name.

A simple, readable approach that returns the first match (safe null checks and trimming):

public Person FindByLastName(string lastName)
{
    if (string.IsNullOrWhiteSpace(lastName)) return null;
    lastName = lastName.Trim();
    return _students?
        .FirstOrDefault(p => string.Equals(p.LastName?.Trim(), lastName, StringComparison.OrdinalIgnoreCase));
}

See the docs for LINQ's FirstOrDefault and StringComparison for behavior details: FirstOrDefault and StringComparison.

If the app does many lookups or you need every match (same last name for multiple students), build an index once and reuse it:

private Dictionary<string, List<Person>> BuildLastNameIndex()
{
    return _students
        .Where(p => !string.IsNullOrWhiteSpace(p.LastName))
        .GroupBy(p => p.LastName.Trim(), StringComparer.OrdinalIgnoreCase)
        .ToDictionary(g => g.Key, g => g.ToList(), StringComparer.OrdinalIgnoreCase);
}

Use index.TryGetValue(key, out var matches) to fetch matches in O(1) time. Dictionary behavior reference: Dictionary<TKey,TValue>.

Practical tips: ensure Person exposes a LastName property (avoid Java-style getLastName() in C#), trim and normalize on insert so searches are consistent, decide whether the method returns a single Person, a list, or throws if ambiguous, and consider thread-safety if _students is shared. As and noted, look at how the collection is populated — convert raw strings to Person objects once and cache them rather than parsing on every search.

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Member Avatar for apegram

You're saying this

foreach (Person search in Page)

Which suggests Page should be something equivalent to an IEnumerable of Person. (List<Person>, IEnumerable<Person>, etc.).

However, in your Page declaration and instantiation, you have this

private List<string> Page;
...
Page = new List<string>();

Hence the error. You have a list of strings based on your declaration & instantiation, but your loop is trying to get a Person.

Edited by apegram because: n/a
Member Avatar for ROTC89

o ok so how would i get it to work with what i have?

Member Avatar for danturn

something like this i would imagine:

foreach (string person in page)
{
   if (person.getLastName().ToLower() == Lname.ToLower())
                {
                    return search;
                }
}
Member Avatar for danturn

I may be getting this very wrong as im a total n00b....

but how are you differentiating between first and last name in your string list?

presumably you're just adding to the list the first/last name as one string?

so each list item is like:

"Dan Turner"
"ROT C89"
or whatever?

so you may want to split each string into parts...

foreach (string person in page)
{
       string [] firstLast = person.Split(' ');
   if (firstLast[1].ToLower() == Lname.ToLower())
                {
                    return person;
                }
}

either than or use

if (person.ToLower().indexOf(Lname.ToLower())>-1)
Edited by danturn because: n/a
Member Avatar for apegram

o ok so how would i get it to work with what i have?

Page needs to be a List<Person> and not a List<string> in order for you to execute your search method. If Page is going to be a List<string> then you will have to change the method. How is Page being populated? I've seen its declaration and instantiation, but I do not see its population.

Step back and look at your total code and make sure your code matches your intent.

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