Convert List to List in C#

Question

I want to convert a List to a List.

Here is my code:

void Convert(List stringList)
{         


        

Answer 1

With Linq:

var intList = stringList.Select(x => int.Parse(x)).ToList();

Answer 2

I would suggest using TryParse(), in case some of the values are not convertible into int. For this I have created an Extension Method. Below is my demo LinqPad code.

void Main()
{
    List<string> sourceList = new List<string> {"1", "2","3", "qwert","4", "5","6", "7","asdf", "9","100", "22"};
    //Dump is a LinqPad only method. Please ignore
    sourceList.ConvertToInt().Dump();
}

static public class HelperMethods
{
    static public List<int> ConvertToInt(this List<string> stringList)
    {
        int x = 0;
        var intList = stringList.Where(str => int.TryParse(str, out x))
                                .Select (str => x)
                                .ToList();
        return intList;

    }
}

In this case, only the numeric int values get parsed and the rest is gracefully ignored. You could built in some error handling / notification if you want to.

/Edit Based on Peter Kiss' suggestion here is a more generic approach based on the IEnumerable interface.

static public IEnumerable<int> ConvertToInt(this IEnumerable<string> source)
{
    int x = 0;
    var result = source.Where(str => int.TryParse(str, out x))
                        .Select (str => x);

    return result;      
}

With this you'd just have to call AsEnumerable() before calling ConvertToInt() The result is of course of type IEnumerable<Int32> and from here on, you can convert it easily into a List by using .ToList() or an array or whatever you need at that point.