FUNDAMEN TA L TYPES: STRING S, A RRAY S, A ND ENUM S in C#.NET

Creating Data Matrix 2d barcode in C#.NET FUNDAMEN TA L TYPES: STRING S, A RRAY S, A ND ENUM S

output, as well as date, time, and currency output, which is dependent on the locale. The following sections provide detailed examples.

The Width Field (or Alignment Specifier)

Listing 5-6 provides some examples of formatting using the width field, including a negative width indicating left justification, and a currency formatting string the c2 following the colon in the Price column, which is ignored when used with a string. Listing 5-6. Formatting Strings Using the Width Field // string_alignment_specifier.cpp using namespace System; int main() { // The format string is interpreted as follows: // { 0, -30 } 30 characters in width, left-justified. // { 1, 10 } 10 characters in width, right-justified. // { 2, 10:c2 } 10 characters in width, currency with 2 decimal places. String^ format = "{0,-30}{1,10}{2,10:c2}"; String^ header = String::Format(format, "Item", "Quantity", "Price"); String^ str1 = str1->Format(format, "Matches, Strike Anywhere", 10, 0.99); String^ str2 = str2->Format(format, "Gloves", 1, 12.50); String^ str3 = str3->Format(format, "Iodine", 1, 4.99); Console::WriteLine(header); Console::WriteLine(str1 + "\n" + str2 + "\n" + str3); } The output of Listing 5-6 on U.S. English systems is as follows: Item Matches, Strike Anywhere Gloves Iodine Quantity 10 1 1 Price $0.99 $12.50 $4.99

Formatting in C runtime functions such as printf involves the use of formatting characters for various data types and, in particular, certain formatting characters for decimal or hexadecimal output, exponential format, and so on. The usual numeric formatting characters from C are supported, as well as additional formats for currency, and a special round-trip format specifically to ensure accurate results when reading the data back in using the Read or ReadLine methods. The code in Listing 5-7 shows the typical use of these formats. The formatting specifier follows the colon after the index (and optional alignment specifier specifying the width of the field) in the format string. In the following example, the alignment specifier is not used, and the index is always zero since we only have one variable to format.

Listing 5-7. Formatting Numeric Strings // string_numerical_formatting.cpp using namespace System; int main() { String^ str; int i = -73000; double dbl = 1005.01; // formats for floating-point types: str = String::Format("Currency format: {0:c2}", dbl); Console::WriteLine(str); str = String::Format("Scientific format: {0:e6}", dbl); Console::WriteLine(str); str = String::Format("Fixed-point format: {0:f6}", dbl); Console::WriteLine(str); str = String::Format("General format: {0:g6}", dbl); Console::WriteLine(str); str = String::Format("Number format: {0:n6}", dbl); Console::WriteLine(str); str = String::Format("Percent format: {0:p6}", dbl); Console::WriteLine(str); str = String::Format("Round-trip format: {0:r6}", dbl); Console::WriteLine(str); // formats for integral types: str = String::Format("Decimal format: {0:d6}", i); Console::WriteLine(str); str = String::Format("General format: {0:g6}", i); Console::WriteLine(str); str = String::Format("Number format: {0:n0}", i); Console::WriteLine(str); str = String::Format("Hexadecimal format: {0:x8}", i); Console::WriteLine(str); }

Here is the output of Listing 5-7: Currency format: $1,005.01 Scientific format: 1.005010e+003 Fixed-point format: 1005.010000 General format: 1005.01 Number format: 1,005.010000 Percent format: 100,501.000000 % Round-trip format: 1005.01 Decimal format: -073000 General format: -73000 Number format: -73,000 Hexadecimal format: fffee2d8

Because String represents an immutable string, for manipulation and editing of strings in-place, you need to use StringBuilder rather than String. StringBuilder contains methods for appending, inserting, removing, and replacing elements of a string (see Listing 5-8). StringBuilder maintains an internal buffer with a given capacity and expands this capacity as the size of the string increases. Listing 5-8. Using StringBuilder // stringbuilder.cpp using namespace System; using namespace System::Text; int main() { // Construct a StringBuilder string with initial contents // "C" and initial capacity 30. StringBuilder^ sb = gcnew StringBuilder("C", 30); sb->Append(gcnew array<Char>{'+','+'}); sb->Append("/CLI."); sb->Insert(0, "I love "); sb->Replace(".","!"); Console::WriteLine( sb->ToString() ); } The output of Listing 5-8 is as follows:

I love C++/CLI!

Refer to the documentation for the .NET Framework or CLI Base Class Library for further information.

You ve seen many examples of rendering primitive types as strings. What about converting from a string to a primitive type System::String implements IConvertible, which means it supports conversions to a variety of types using functions such as ToBoolean, ToInt32, and so on. Also, the object wrappers for the primitive types support the ability to parse strings. There are static methods called Parse on the classes for the primitive types that take a string to be parsed as a parameter and return an object of the numeric type. Listing 5-9 provides some examples. Listing 5-9. Converting Strings to Primitive Types // convert_and_parse.cpp using namespace System; int main() { String^ str1 = "115"; String^ str2 = "1.4e-12"; // Parse the string to get the integer value. int i = Int32::Parse(str1); // Get the double value. double x = Double::Parse(str2); // Use Convert class to convert the value. int j = Convert::ToInt32(str1); double y = Convert::ToDouble(str2); // Exception handlers may be used to catch parse failures and overflows. try { int k = Int32::Parse("bad format"); } catch(FormatException^ e) { Console::WriteLine("Exception occurred! {0}", e->Message ); } }