My question is part of this problem:
I receive a collection of id's from a form. I need to get the keys, convert them to integers and select the matching records from the DB.
[HttpPost]
public ActionResult Report(FormCollection collection)
{
var listofIDs = collection.AllKeys.ToList();
// List<string> to List<int>
List<Dinner> dinners = new List<Dinner>();
dinners= repository.GetDinners(listofIDs);
return View(dinners);
}
listofIDs.Select(int.Parse).ToList()
listofIDs is an IQueryable<string> that has not been executed. Execute it first with ToList() before you do the conversion: listofIDs.ToList().Select(int.Parse).ToList()
Here is a safe variant that filters out invalid ints:
List<int> ints = strings
.Select(s => Int32.TryParse(s, out int n) ? n : (int?)null)
.Where(n => n.HasValue)
.Select(n => n.Value)
.ToList();
It uses an out variable introduced with C#7.0.
This other variant returns a list of nullable ints where null entries are inserted for invalid ints (i.e. it preserves the original list count):
List<int?> nullableInts = strings
.Select(s => Int32.TryParse(s, out int n) ? n : (int?)null)
.ToList();
Using Linq ...
List<string> listofIDs = collection.AllKeys.ToList();
List<int> myStringList = listofIDs.Select(s => int.Parse(s)).ToList();
What no TryParse? Safe LINQ version that filters out invalid ints (for C# 6.0 and below):
List<int> ints = strings
.Select(s => { int i; return int.TryParse(s, out i) ? i : (int?)null; })
.Where(i => i.HasValue)
.Select(i => i.Value)
.ToList();
credit to Olivier Jacot-Descombes for the idea and the C# 7.0 version.
Using Linq:
var intList = stringList.Select(s => Convert.ToInt32(s)).ToList()
I know it's old post, but I thought this is a good addition:
You can use List<T>.ConvertAll<TOutput>
List<int> integers = strings.ConvertAll(s => Int32.Parse(s));
List<int> integers = strings.ConvertAll(int.Parse);Convert string value into integer list
var myString = "010";
int myInt;
List<int> B = myString.ToCharArray().Where(x => int.TryParse(x.ToString(), out myInt)).Select(x => int.Parse(x.ToString())).ToList();
This may be overkill for this simple problem. But for Try-Do methods in connection with Linq, I tend to use anonymous classes for more expressive code. It is similar to the answers from Olivier Jacot-Descombes and BA TabNabber:
List<int> ints = strings
.Select(idString => new { ParseSuccessful = int.TryParse(idString, out var id), Value = id })
.Where(id => id.ParseSuccessful)
.Select(id => id.Value)
.ToList();
This is the simplest way, I think:
var listOfStrings = (new [] { "4", "5", "6" }).ToList();
var listOfInts = listOfStrings.Select<string, int>(q => Convert.ToInt32(q));
List<string> sss = new List<string>(); IEnumerable<int> test1 = sss.Select<string, int>(x => Convert.ToInt32(x)); but this does not: IEnumerable<int> test2 = sss.Select<string, int>(Convert.ToInt32); The error is ambiguous call between the string,int,int and string,int versions of Select.Another way to accomplish this would be using a linq statement. The recomended answer did not work for me in .NetCore2.0. I was able to figure it out however and below would also work if you are using newer technology.
[HttpPost]
public ActionResult Report(FormCollection collection)
{
var listofIDs = collection.ToList().Select(x => x.ToString());
List<Dinner> dinners = new List<Dinner>();
dinners = repository.GetDinners(listofIDs);
return View(dinners);
}
You can use it via LINQ
var selectedEditionIds = input.SelectedEditionIds.Split(",").ToArray()
.Where(i => !string.IsNullOrWhiteSpace(i)
&& int.TryParse(i,out int validNumber))
.Select(x=>int.Parse(x)).ToList();
intList = Array.ConvertAll(stringList, int.Parse).ToList();
This converts array of string to array of long. It returns number of successfully converted values.
public static int strv_to_longv(string[] src, int src_offset, long[] dst, int dst_offset)
{
int i = src_offset;
int j = dst_offset;
int ni = src.Length;
int nj = dst.Length;
while ((i < ni) && (j < nj))
{
j += long.TryParse(src[i], out dst[j]) ? 1 : 0;
i++;
}
return j;
}
var line = "lemon 4 grape 1 garlic 77";
string[] words = line.Split(' ');
long[] longs = new long[10];
int l = strv_to_longv(words, 1, longs, 0);
//longs will be equal {4, 1, 77}
//l will be equal 3
public List<int> ConvertStringListToIntList(List<string> list)
{
List<int> resultList = new List<int>();
for (int i = 0; i < list.Count; i++)
resultList.Add(Convert.ToInt32(list[i]));
return resultList;
}
yourEnumList.Select(s => (int)s).ToList()
