CODEWITHSUNDEEP
c#linq
user2818430
user2818430

Reputation: 6029

List<string> get item that starts with Name= using LINQ

How can i retrieve from a List<string> the item(value) that starts with Name=

If the list contains the values:

Name=Jhon Smith
Age=20
Location=CityName

I want to get the value Jhon Smith.

I do know how to traditionally loop through the list using foreach and have a condition if value starts with Name= ... but I'm not that good with LINQ.

Upvotes: 0

Views: 11930

Answers (4)

Dariusz Woźniak
Dariusz Woźniak

Reputation: 10350

A slightly modernized and updated version that:

  • uses C# indexer
  • does not use the magic value of 5 (which is "Name=".Length):
var list = new List<string> { "Name=Jhon Smith", "Age=20", "Location=CityName" };

const string namePrefix = "Name=";
string? name = list.FirstOrDefault(s => s.StartsWith(namePrefix));
name = name?[namePrefix.Length..]; // Jhon Smith

Upvotes: 0

BartoszKP
BartoszKP

Reputation: 35891

Use Single or SingleOrDefault like this:

var result = list.Single(s => s.StartsWith("Name=")).Substring(5);

or

string result = string.Empty;
var element = list.SingleOrDefault(s => s.StartsWith("Name="));

if (element == null)
{
    //"Name=" not present, throw an exception
}

result = element.Substring(5);

or similarly with First, or FirstOrDefault depending on what you exactly want.

There was another interesting answer by the user canon, but was deleted (I don't know why):

var result = list
              .Where(x => x.StartsWith("Name="))
              .Select(x => x.Substring(5))
              .FirstOrDefault();

Its advantage is that it won't throw regardless of the input data.

Upvotes: 3

Erik A. Brandstadmoen
Erik A. Brandstadmoen

Reputation: 10588

This will throw an exception if there is no such element in the collection. You can use FirstOrDefault and check if you get null or an element to check whether there was a match or not. 

list.First(x => x.StartsWith("Name=")).Substring(5)

This won't throw an exception: 

var prefix = "Name=";
var elem = list.FirstOrDefault(item => item.StartsWith(prefix));
if (elem != null) {
    return elem.Substring(prefix.Length)
} else {
    return null;
}

Upvotes: 6

Dai
Dai

Reputation: 155065

String match = list.FirstOrDefault( str => str.IndexOf("Name=", StringComparison.InvariantCulture) > -1 );
return match.Substring("Name=".Length);

Upvotes: 1

Related Questions