How to combine and compare string collections (LINQ) (C#)
This example shows how to merge files that contain lines of text and then sort the results. Specifically, it shows how to perform a simple concatenation, a union, and an intersection on the two sets of text lines.
To set up the project and the text files
Copy these names into a text file that is named names1.txt and save it in your project folder:
Bankov, Peter Holm, Michael Garcia, Hugo Potra, Cristina Noriega, Fabricio Aw, Kam Foo Beebe, Ann Toyoshima, Tim Guy, Wey Yuan Garcia, Debra
Copy these names into a text file that is named names2.txt and save it in your project folder. Note that the two files have some names in common.
Liu, Jinghao Bankov, Peter Holm, Michael Garcia, Hugo Beebe, Ann Gilchrist, Beth Myrcha, Jacek Giakoumakis, Leo McLin, Nkenge El Yassir, Mehdi
Example
class MergeStrings
{
static void Main(string[] args)
{
//Put text files in your solution folder
string[] fileA = System.IO.File.ReadAllLines(@"../../../names1.txt");
string[] fileB = System.IO.File.ReadAllLines(@"../../../names2.txt");
//Simple concatenation and sort. Duplicates are preserved.
IEnumerable<string> concatQuery =
fileA.Concat(fileB).OrderBy(s => s);
// Pass the query variable to another function for execution.
OutputQueryResults(concatQuery, "Simple concatenate and sort. Duplicates are preserved:");
// Concatenate and remove duplicate names based on
// default string comparer.
IEnumerable<string> uniqueNamesQuery =
fileA.Union(fileB).OrderBy(s => s);
OutputQueryResults(uniqueNamesQuery, "Union removes duplicate names:");
// Find the names that occur in both files (based on
// default string comparer).
IEnumerable<string> commonNamesQuery =
fileA.Intersect(fileB);
OutputQueryResults(commonNamesQuery, "Merge based on intersect:");
// Find the matching fields in each list. Merge the two
// results by using Concat, and then
// sort using the default string comparer.
string nameMatch = "Garcia";
IEnumerable<String> tempQuery1 =
from name in fileA
let n = name.Split(',')
where n[0] == nameMatch
select name;
IEnumerable<string> tempQuery2 =
from name2 in fileB
let n2 = name2.Split(',')
where n2[0] == nameMatch
select name2;
IEnumerable<string> nameMatchQuery =
tempQuery1.Concat(tempQuery2).OrderBy(s => s);
OutputQueryResults(nameMatchQuery, $"Concat based on partial name match \"{nameMatch}\":");
}
static void OutputQueryResults(IEnumerable<string> query, string message)
{
Console.WriteLine(System.Environment.NewLine + message);
foreach (string item in query)
{
Console.WriteLine(item);
}
Console.WriteLine("{0} total names in list", query.Count());
}
}
/* Output:
Simple concatenate and sort. Duplicates are preserved:
Aw, Kam Foo
Bankov, Peter
Bankov, Peter
Beebe, Ann
Beebe, Ann
El Yassir, Mehdi
Garcia, Debra
Garcia, Hugo
Garcia, Hugo
Giakoumakis, Leo
Gilchrist, Beth
Guy, Wey Yuan
Holm, Michael
Holm, Michael
Liu, Jinghao
McLin, Nkenge
Myrcha, Jacek
Noriega, Fabricio
Potra, Cristina
Toyoshima, Tim
20 total names in list
Union removes duplicate names:
Aw, Kam Foo
Bankov, Peter
Beebe, Ann
El Yassir, Mehdi
Garcia, Debra
Garcia, Hugo
Giakoumakis, Leo
Gilchrist, Beth
Guy, Wey Yuan
Holm, Michael
Liu, Jinghao
McLin, Nkenge
Myrcha, Jacek
Noriega, Fabricio
Potra, Cristina
Toyoshima, Tim
16 total names in list
Merge based on intersect:
Bankov, Peter
Holm, Michael
Garcia, Hugo
Beebe, Ann
4 total names in list
Concat based on partial name match "Garcia":
Garcia, Debra
Garcia, Hugo
Garcia, Hugo
3 total names in list
*/
Compiling the Code
Create a C# console application project, with using
directives for the System.Linq and System.IO namespaces.
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