C# in Depth

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Real-life example: iterating over ranges175■ We want to be able to find out whether a particular value is within the range.■ We want to be able to iterate through the range easily.The last point is obviously the most important one for this chapter, but the othersshape the fundamental decisions and ask further questions. In particular, it seemsobvious that this should use generics, but should we allow any type to be used for thebounds of the range, using an appropriate IComparer, or should we only allow typesthat implement IComparable, where T is the same type? When we’re iterating, howdo we move from one value to another? Should we always have to be able to iterateover a range, even if we’re only interested in the other aspects? Should we be able tohave a “reverse” range (in other words, one with a start that is greater than the end,and therefore counts down rather than up)? Should the start and end points be exclusiveor inclusive?All of these are important questions, and the normal answers would promote flexibilityand usefulness of the type—but our overriding priority here is to keep thingssimple. So:■ We’ll make comparisons simple by constraining the range’s type parameter T toimplement IComparable.■ We’ll make the class abstract and require a GetNextValue method to be implemented,which will be used during iteration.■ We won’t worry about the idea of a range that can’t be iterated over.■ We won’t allow reverse ranges (so the end value must always be greater than orequal to the start value).■ Start and end points will both be inclusive (so both the start and end points areconsidered to be members of the range). One consequence of this is that wecan’t represent an empty range.The decision to make it an abstract class isn’t as limiting as it possibly sounds—itmeans we’ll have derived classes like Int32Range and DateTimeRange that allow you tospecify the “step” to use when iterating. If we ever wanted a more general range, wecould always create a derived type that allows the step to be specified as a Converterdelegate. For the moment, however, let’s concentrate on the base type. With all therequirements specified, 8 we’re ready to write the code.6.3.3 Implementation using iterator blocksWith C# 2, implementing this (fairly limited) Range type is remarkably easy. The hardestpart (for me) is remembering how IComparable.CompareTo works. The trick I usuallyuse is to remember that if you compare the return value with 0, the result is the sameas applying that comparison operator between the two values involved, in the orderthey’re specified. So x.CompareTo(y) < 0 has the same meaning as x < y, for example.8If only real life were as simple as this. We haven’t had to get project approval and specification sign-off froma dozen different parties, nor have we had to create a project plan complete with resource requirements.Beautiful!Licensed to Rhona Hadida
176 CHAPTER 6 Implementing iterators the easy wayListing 6.8 is the complete Range class, although we can’t quite use it yet as it’s stillabstract.Listing 6.8The abstract Range class allowing flexible iteration over its valuesusing System;using System.Collections;using System.Collections.Generic;public abstract class Range : IEnumerablewhere T : IComparable{Breadonly T start;readonly T end;public Range(T start, T end) CPrevents{“reversed”if (start.CompareTo(end) > 0) ranges{throw new ArgumentOutOfRangeException();}this.start = start;this.end = end;}public T Start{get { return start; }}public T End{get { return end; }}public bool Contains(T value){return value.CompareTo(start) >= 0 &&value.CompareTo(end)
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C# in DepthLicensed to Rhona Hadida
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C# in DepthJON SKEETMANNINGGreenwic
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Licensed to Rhona Hadida
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Licensed to Rhona Hadida
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xCONTENTS1.3 The .NET platform 24Di
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xiiCONTENTS5.4 Inline delegate acti
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xivCONTENTS9.4 Changes to type infe
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xviCONTENTS13.2 Delegation as the n
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xviiiFOREWORDOf the latter kind, th
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xxPREFACEdidn’t start using C#2 u
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xxiiACKNOWLEDGMENTSThe aforemention
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xxivABOUT THIS BOOKwant to become e
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xxviABOUT THIS BOOKSQL statements.
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about the cover illustrationThe cap
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xxxCOMMENTS FROM THE TECH REVIEWThi
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Chapter 1 presents a bird’s-eye v
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4 CHAPTER 1 The changing face of C#
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10 CHAPTER 1 The changing face of C
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Core foundations:building on C# 1Th
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34 CHAPTER 2 Core foundations: buil
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C# 2 and 3: new features on a solid
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C# 2 and 3: new features on a solid
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Summary59Listing 2.7 shows a number
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Part 2C#2:solving the issuesof C#1I
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Parameterizedtyping with genericsTh
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Simple generics for everyday use65o
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Simple generics for everyday use67I
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Simple generics for everyday use69t
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Simple generics for everyday use71N
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Simple generics for everyday use73}
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Beyond the basics75parameters. You
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Beyond the basics77NOTEC# vs. CLI s
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Beyond the basics79combined togethe
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Beyond the basics813.3.3 Implementi
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Beyond the basics83derive from a pa
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Advanced generics85implement IEquat
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Advanced generics87within another,
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Advanced generics89ArrayListobject[
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Advanced generics91}{}return new Co
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Advanced generics93Listing 3.10Usin
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Advanced generics95REFLECTING GENER
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Generic collection classes in .NET
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Limitations of generics in C# and o
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Summary111My personal opinion is th
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What do you do when you just don’
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System.Nullable and System.Nullable
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C# 2’s syntactic sugar for nullab
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C# 2’s syntactic sugar for nullab
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Page 162 and 163: Novel uses of nullable types131part
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Page 166 and 167: Novel uses of nullable types135}{}i
Page 168 and 169: Fast-tracked delegatesThis chapter
Page 170 and 171: Saying goodbye to awkward delegate
Page 172 and 173: Covariance and contravariance141met
Page 174 and 175: Covariance and contravariance143som
Page 176 and 177: Inline delegate actions with anonym
Page 182 and 183: Capturing variables in anonymous me
Page 192 and 193: Implementingiterators the easy wayT
Page 194 and 195: C# 1: the pain of handwritten itera
Page 196 and 197: C# 2: simple iterators with yield s
Page 204 and 205: Real-life example: iterating over r
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Page 210 and 211: Pseudo-synchronous code with the Co
Page 212 and 213: Summary181(without using a dedicate
Page 214 and 215: Concluding C# 2:the final featuresT
Page 216 and 217: Partial types185C# 2 allows more th
Page 218 and 219: Partial types187code generator can
Page 220 and 221: Partial types189Listing 7.2A partia
Page 222 and 223: Static classes191}public static str
Page 224 and 225: Namespace aliases193same syntax is
Page 226 and 227: Namespace aliases195Listing 7.6usin
Page 228 and 229: Pragma directives197}}Console.Write
Page 230 and 231: Fixed-size buffers in unsafe code19
Page 232 and 233: Exposing internal members to select
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Page 236 and 237: Part 3C# 3—revolutionizinghow we
Page 238 and 239: Cutting fluffwith a smart compilerT
Page 240 and 241: Automatically implemented propertie
Page 242 and 243: Implicit typing of local variables2
Page 244 and 245: Implicit typing of local variables2
Page 246 and 247: Simplified initialization215simple
Page 248 and 249: Simplified initialization217The par
Page 250 and 251: Simplified initialization219CREATIN
Page 252 and 253: Simplified initialization221Home =
Page 254 and 255: Implicitly typed arrays2238.4 Impli
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Anonymous types225new { Name = "Hol
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Anonymous types227That certainly wo
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Summary229typed local variables—a
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Lambda expressions and expression t
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Lambda expressions as delegates233L
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Simple examples using List and even
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Simple examples using List and even
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Expression trees239code to run on y
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Expression trees241So, what’s the
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Expression trees243the tree and how
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Changes to type inference and overl
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Summary253find the better conversio
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Extension methodsThis chapter cover
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Life before extension methods257Sys
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Extension method syntax259extension
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Extension method syntax26110.2.3 Ho
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Extension methods in .NET 3.5263pub
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Extension methods in .NET 3.5265ret
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Extension methods in .NET 3.5267as
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Extension methods in .NET 3.5269Now
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Usage ideas and guidelines271extens
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Usage ideas and guidelines273those
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Query expressionsand LINQ to Object
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Introducing LINQ277the extension me
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Introducing LINQ279Figure 11.1 show
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Introducing LINQ281flexible. In par
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Simple beginnings: selecting elemen
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Filtering and ordering a sequence29
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Filtering and ordering a sequence29
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Let clauses and transparent identif
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Joins29711.5 JoinsEach part of the
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Joins299from defect inSampleData.Al
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Joins30111.5.2 Group joins with joi
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Joins303foreach (var grouped in que
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Joins305from user inSampleData.AllU
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Groupings and continuations307In ju
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Groupings and continuations309from
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Groupings and continuations311perso
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Summary31311.7 SummaryIn this chapt
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LINQ to SQL315LINQ to DataSet and L
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LINQ to SQL317■ I changed the typ
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LINQ to SQL319each of type Table fo
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LINQ to SQL321FROM [dbo].[Defect] A
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LINQ to SQL323FROM [dbo].[Notificat
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LINQ to SQL325using (var context =
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Translations using IQueryable and I
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LINQ to DataSet335where defect.Fiel
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LINQ to DataSet337Creating and popu
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LINQ to XML339■ Create a document
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LINQ to XML341You can nest query ex
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LINQ to XML343need the string form,
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LINQ beyond .NET 3.5345Listing 12.1
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LINQ beyond .NET 3.5347LINQ TO ACTI
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LINQ beyond .NET 3.5349All of the L
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Summary351you look back at all the
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The changing nature of language pre
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Delegation as the new inheritance35
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Life in a parallel universe357Array
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appendix:LINQ standardquery operato
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Conversion361Cast and OfType conver
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Equality operations363A.4 Element o
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Joins365A.7 GroupingThere are two g
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Quantifiers367Table A.9Partitioning
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Sorting369For the examples of these
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indexSymbols!= 82with generics 76#p
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INDEX 373C# (continued)influences 1
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INDEX 375confusion 150, 222over cap
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INDEX 377Document Object Model (DOM
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INDEX 379fully qualified type name
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INDEX 381interfaces (continued)no c
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INDEX 383List`1 93lists 278local va
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INDEX 385Nullable (continued)Value
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INDEX 387RRails 22random access 102
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INDEX 389Standard Query Operators (
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INDEX 391type parameters (continued
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C# in Depth

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