27: Common Array Coding Errors in Visual C#

Painting Quick Response Code in Visual C# 27: Common Array Coding Errors
TABLE 27: Common Array Coding Errors
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Common Mistake
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int numbers[];
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Error Description
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Corrected Code
Quick Response Code Encoder In Visual Basic .NET
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int[] numbers;
Encoding Bar Code In C#
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The square braces for declaring an array appear after the data type, not after the variable identifier When assigning an array after declaration, it is necessary to use the new keyword and then specify the data type It is not possible to specify the array size as part of the variable declaration The array size is required at initialization time unless an array literal is provided The array size is specified as 3, but there are no elements in the array literal The array size must match the number of elements in the array literal Array indexes start at zero Therefore, the last item is one less than the array size (Note that this is a runtime error, not a compile-time error)
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int[] numbers; numbers = {42, 84, 168 };
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int[] numbers; numbers = new int[]{ 42, 84, 168 } int[] numbers = { 42, 84, 168 }; int[] numbers = new int[3]; int[] numbers = new int[3] { 42, 84, 168 };
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int[3] numbers = { 42, 84, 168 }; int[] numbers = new int[]; int[] numbers = new int[3]{}
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int[] numbers = new int[3]; ConsoleWriteLine( numbers[3]);
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int[] numbers = new int[3]; ConsoleWriteLine( numbers[2]);
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Continues
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TABLE 27: Common Array Coding Errors (Continued)
EAN13 Scanner In VS .NET
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Common Mistake
Generating Code 39 Extended In Java
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int[] numbers = new int[3]; numbers[numbersLength] = 42; int[] numbers; ConsoleWriteLine( numbers[0]); int[,] numbers = { {42}, {84, 42} }; int[][] numbers = { {42, 84}, {84, 42} };
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Error Description
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Corrected Code
Read Code 39 Extended In Visual Studio .NET
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int[] numbers = new int[3]; numbers[numbersLength-1] = 42; int[] numbers = {42, 84}; ConsoleWriteLine( numbers[0]); int[,] numbers = { {42, 168}, {84, 42} }; int[][] numbers = { new int[]{42, 84}, new int[]{84, 42} };
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Same as previous error: 1 needs to be subtracted from the Length to access the last element (Note that this is a runtime error, not a compile-time error)
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numbers has not yet been assigned an
instantiated array, and therefore, it cannot be accessed Multidimensional arrays must be structured consistently Jagged arrays require instantiated arrays to be specified for the arrays within the array
Summary
SUMMARY
Even for experienced programmers, C# introduces several new programming constructs For example, as part of the section on data types, this chapter covered the type decimal that can be used accurately for financial calculations In addition, the chapter introduced the fact that the Boolean type, bool, does not convert implicitly to an integer, thereby preventing the mistaken use of the assignment operator in a conditional expression Other unique characteristics of C# from many of its predecessors are the @ verbatim string qualifier that forces a string to ignore the escape character and the fact that the string data type is immutable To convert data types between each other C# includes the cast operator in both an explicit and an implicit form In the following chapters, you will learn how to define both cast operators on custom types This chapter closed with coverage of C# syntax for arrays, along with the various means of manipulating arrays For many developers, the syntax can become rather daunting at first, so the section included a list of the common errors associated with coding arrays The next chapter looks at expressions and control flow statements The if statement, which appeared a few times toward the end of this chapter, is discussed as well
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Operators and Control Flow
you will learn about operators and control flow statements Operators provide syntax for performing different calculations or actions appropriate for the operands within the calculation Control flow statements provide the means for conditional logic within a program or looping over a section of code multiple times After introducing the if control flow statement, the chapter looks at the concept of Boolean expressions, which are embedded within many control flow statements Included is mention of how integers will not cast (even explicitly) to bool and the
#if, #elif, #else, and #endif #define and #undef #error and #warning #pragma nowarn:<warn list> #line #region/#endregion
N THIS CHAPTER,