How to Convert a Comma-Separated String into a List of Integers in C#

This is a simple task and differs from parsing complex CSV data (with rows of comma-separated values). Here, you can use string.Split(",") to break the string into individual components and then convert each one to an integer.

For example, How to parser a Comma-Separated String into a List of Integers using LINQ in C#

using System.Linq;

var csv = "5,10,15";

var ints = csv.Split(",").Select(i => Int32.Parse(i)).ToList();

Console.WriteLine($"We have {ints.Count} ints");

This will output:

We have 3 ints

Although this example demonstrates parsing integers, you can easily modify it to parse any type (such as decimal, DateTime, etc.). You can use Convert.ChangeType() to convert the string into any target type, or use the specific type’s conversion method.

Let’s say you want to parse the comma-separated values and only add valid integers to the list, avoiding errors. You can do this by splitting the string, iterating through the components, and using Int32.TryParse instead of Int32.Parse.

List<int> ParseInts(string csv)
{
    var ints = new List<int>();

    if (string.IsNullOrEmpty(csv))
        return ints;

    foreach (string s in csv.Split(","))
    {
        if (Int32.TryParse(s, out int i))
            ints.Add(i);
    }

    return ints;
}

You can then use this method to handle different cases:

var first = ParseInts("5,10,15");
Console.WriteLine($"First has {first.Count} valid ints");

var second = ParseInts("");
Console.WriteLine($"Second has {second.Count} valid ints");

var third = ParseInts("5,10,abc,20");
Console.WriteLine($"Third has {third.Count} valid ints");

Output:

First has 3 valid ints
Second has 0 valid ints
Third has 3 valid ints

Notice that the invalid entry abc was ignored.

Parsing into a HashSet

If you need to store only unique integers and perform fast lookups, you can use a HashSet instead of a List.

To convert the parsed integers into a HashSet, you can use the LINQ ToHashSet() method:

using System.Linq;

var csv = "5,10,15,5";

var intSet = csv.Split(",").Select(i => Int32.Parse(i)).ToHashSet();

Console.WriteLine($"Set has 5? {intSet.Contains(5)}");
Console.WriteLine($"Set has 100? {intSet.Contains(100)}");

This will output:

Set has 5? True
Set has 100? False

In this example, intSet only contains unique values, and duplicates (like the second "5") are removed.