Linq query - find strings based upon first letter b/w two ranges
We have a list containing names of countries. We need to find names of countries from list b/w two letters. Like names of all countries with name starting b/w A-G and s开发者_JAVA百科o on. We create following linq query but its ugly.
var countryAG = from elements in countryList
where elements.StartsWith("A") ||
elements.StartsWith("B") ||
elements.StartsWith("C") ||
elements.StartsWith("D") ||
elements.StartsWith("E") ||
elements.StartsWith("F") ||
elements.StartsWith("G") ||
elements.StartsWith("H")
select elements;
where countryList is created in C#
List< string> countryList = new List< string>();
Any help or any other efficient way to accomplish above task?
var countryAG = from elements in countryList
where elements[0] >= 'A' && elements[0] <= 'H'
select elements;
Chars are just numbers really, thus you can compare them as such
I can't test it right now, but I would try
countryList.Where((s) => s[0] <= 'A' && s[0] >= 'G');
You could use a prefix list and then use the prefix list for comparison - this way you can easily use different prefix lists based on what range you are interested in:
List<string> prefixList = new List<string>() { "A", "B", "C", "D", "E", "F", "G" };
var countryAG = countryList.Where( x=> prefixList.Any( p => x.StartsWith(p)));
Try
char[] startingLetters = new char[] {'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H'};
var countryAG =
from elements in countryList
where elements.IndexOfAny(startingLetters, 0, 1) == 0
select elements;
See here for information on IndexOfAny
.
Try use this code:
var start = "a";
var end = "g";
var regex = new Regex(string.Format("^[{0}-{1}]", start, end));
var result = list.Where(x => regex.Match(x.ToLowerInvariant()).Success);
'start' and 'end' are static as an example.
I have two extension functions:
public static IEnumerable<char> Range(char start, char end)
{
return Enumerable.Range((int)start, (int)end - (int)start + 1).Select(i => (char)i);
}
which creates a range of characters, and
public static bool In(this string source, IEnumerable<string> collection)
{
return collection.Contains(source);
}
which is just the inverse of Contains
, mostly for readability.
Together I can do:
where elements[0].In(Range('a', 'f')))
List<string> mainList = new List<string>()
{
"A","B","DD","EE","F","G","EE","CC","DD","Q","R","CC"
};
List<string> searchList = new List<string>() { "DD", "EE", "CC" };
var finalList = mainList.Where(x => searchList.Any(p => p == x)).ToList();
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