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https://github.com/markjprice/cs11dotnet7.git
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96 lines
2.7 KiB
C#
96 lines
2.7 KiB
C#
// a string array is a sequence that implements IEnumerable<string>
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string[] names = new[] { "Michael", "Pam", "Jim", "Dwight",
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"Angela", "Kevin", "Toby", "Creed" };
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SectionTitle("Deferred execution");
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// Question: Which names end with an M?
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// (written using a LINQ extension method)
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var query1 = names.Where(name => name.EndsWith("m"));
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// Question: Which names end with an M?
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// (written using LINQ query comprehension syntax)
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var query2 = from name in names where name.EndsWith("m") select name;
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// Answer returned as an array of strings containing Pam and Jim
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string[] result1 = query1.ToArray();
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// Answer returned as a list of strings containing Pam and Jim
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List<string> result2 = query2.ToList();
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// Answer returned as we enumerate over the results
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foreach (string name in query1)
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{
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WriteLine(name);
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}
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SectionTitle("Writing queries");
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// Where requires a Func<T, T> delegate instance...
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// var query = names.Where(
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// new Func<string, bool>(NameLongerThanFour));
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// ...but the compiler can create it for us...
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// var query = names.Where(NameLongerThanFour);
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// ...or we can use a lambda expression.
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IOrderedEnumerable<string> query = names
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.Where(name => name.Length > 4)
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.OrderBy(name => name.Length)
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.ThenBy(name => name);
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foreach (string item in query)
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{
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WriteLine(item);
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}
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SectionTitle("Filtering by type");
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List<Exception> exceptions = new()
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{
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new ArgumentException(),
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new SystemException(),
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new IndexOutOfRangeException(),
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new InvalidOperationException(),
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new NullReferenceException(),
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new InvalidCastException(),
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new OverflowException(),
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new DivideByZeroException(),
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new ApplicationException()
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};
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IEnumerable<ArithmeticException> arithmeticExceptionsQuery =
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exceptions.OfType<ArithmeticException>();
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foreach (ArithmeticException exception in arithmeticExceptionsQuery)
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{
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WriteLine(exception);
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}
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string[] cohort1 = new[]
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{ "Rachel", "Gareth", "Jonathan", "George" };
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string[] cohort2 = new[]
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{ "Jack", "Stephen", "Daniel", "Jack", "Jared" };
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string[] cohort3 = new[]
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{ "Declan", "Jack", "Jack", "Jasmine", "Conor" };
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SectionTitle("The cohorts");
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Output(cohort1, "Cohort 1");
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Output(cohort2, "Cohort 2");
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Output(cohort3, "Cohort 3");
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SectionTitle("Set operations");
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Output(cohort2.Distinct(), "cohort2.Distinct()");
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Output(cohort2.DistinctBy(name => name.Substring(0, 2)),
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"cohort2.DistinctBy(name => name.Substring(0, 2)):");
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Output(cohort2.Union(cohort3), "cohort2.Union(cohort3)");
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Output(cohort2.Concat(cohort3), "cohort2.Concat(cohort3)");
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Output(cohort2.Intersect(cohort3), "cohort2.Intersect(cohort3)");
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Output(cohort2.Except(cohort3), "cohort2.Except(cohort3)");
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Output(cohort1.Zip(cohort2, (c1, c2) => $"{c1} matched with {c2}"),
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"cohort1.Zip(cohort2)");
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