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Double转化为String时的保留位数及格式
有时需要将程序中的数据写入到文件中进行保存，这时候就涉及到数据的字符串格式问题。
下面介绍Double转化为String时如何设置保留位数及格式，示例来自官方资料，本文用于日后快速查询。
Double.ToString Method官方资料
double[] numbers= {1054.32179, -195489100.8377, 1.0437E21, -1.0573e-05};string[] specifiers = { "C", "E", "e", "F", "G", "N", "P", "R", "#,000.000", "0.###E-000", "000,000,000,000.00###" };foreach (double number in numbers){ Console.WriteLine("Formatting of {0}:", number); foreach (string specifier in specifiers) { Console.WriteLine(" {0,-22} {1}", specifier + ":", number.ToString(specifier)); // Add precision specifiers from 0 to 3. if (specifier.Length == 1 & ! specifier.Equals("R")) { for (int precision = 0; precision <= 3; precision++) { string pSpecifier = String.Format("{0}{1}", specifier, precision); Console.WriteLine(" {0,-22} {1}", pSpecifier + ":", number.ToString(pSpecifier)); } Console.WriteLine(); } } Console.WriteLine();}// The example displays the following output to the console:// Formatting of 1054.32179:// C: $1,054.32// C0: $1,054// C1: $1,054.3// C2: $1,054.32// C3: $1,054.322// // E: 1.054322E+003// E0: 1E+003// E1: 1.1E+003// E2: 1.05E+003// E3: 1.054E+003// // e: 1.054322e+003// e0: 1e+003// e1: 1.1e+003// e2: 1.05e+003// e3: 1.054e+003// // F: 1054.32// F0: 1054// F1: 1054.3// F2: 1054.32// F3: 1054.322// // G: 1054.32179// G0: 1054.32179// G1: 1E+03// G2: 1.1E+03// G3: 1.05E+03// // N: 1,054.32// N0: 1,054// N1: 1,054.3// N2: 1,054.32// N3: 1,054.322// // P: 105,432.18 %// P0: 105,432 %// P1: 105,432.2 %// P2: 105,432.18 %// P3: 105,432.179 %// // R: 1054.32179// #,000.000: 1,054.322// 0.###E-000: 1.054E003// 000,000,000,000.00###: 000,000,001,054.32179// // Formatting of -195489100.8377:// C: ($195,489,100.84)// C0: ($195,489,101)// C1: ($195,489,100.8)// C2: ($195,489,100.84)// C3: ($195,489,100.838)// // E: -1.954891E+008// E0: -2E+008// E1: -2.0E+008// E2: -1.95E+008// E3: -1.955E+008// // e: -1.954891e+008// e0: -2e+008// e1: -2.0e+008// e2: -1.95e+008// e3: -1.955e+008// // F: -195489100.84// F0: -195489101// F1: -195489100.8// F2: -195489100.84// F3: -195489100.838// // G: -195489100.8377// G0: -195489100.8377// G1: -2E+08// G2: -2E+08// G3: -1.95E+08// // N: -195,489,100.84// N0: -195,489,101// N1: -195,489,100.8// N2: -195,489,100.84// N3: -195,489,100.838// // P: -19,548,910,083.77 %// P0: -19,548,910,084 %// P1: -19,548,910,083.8 %// P2: -19,548,910,083.77 %// P3: -19,548,910,083.770 %// // R: -195489100.8377// #,000.000: -195,489,100.838// 0.###E-000: -1.955E008// 000,000,000,000.00###: -000,195,489,100.8377// // Formatting of 1.0437E+21:// C: $1,043,700,000,000,000,000,000.00// C0: $1,043,700,000,000,000,000,000// C1: $1,043,700,000,000,000,000,000.0// C2: $1,043,700,000,000,000,000,000.00// C3: $1,043,700,000,000,000,000,000.000// // E: 1.043700E+021// E0: 1E+021// E1: 1.0E+021// E2: 1.04E+021// E3: 1.044E+021// // e: 1.043700e+021// e0: 1e+021// e1: 1.0e+021// e2: 1.04e+021// e3: 1.044e+021// // F: 1043700000000000000000.00// F0: 1043700000000000000000// F1: 1043700000000000000000.0// F2: 1043700000000000000000.00// F3: 1043700000000000000000.000// // G: 1.0437E+21// G0: 1.0437E+21// G1: 1E+21// G2: 1E+21// G3: 1.04E+21// // N: 1,043,700,000,000,000,000,000.00// N0: 1,043,700,000,000,000,000,000// N1: 1,043,700,000,000,000,000,000.0// N2: 1,043,700,000,000,000,000,000.00// N3: 1,043,700,000,000,000,000,000.000// // P: 104,370,000,000,000,000,000,000.00 %// P0: 104,370,000,000,000,000,000,000 %// P1: 104,370,000,000,000,000,000,000.0 %// P2: 104,370,000,000,000,000,000,000.00 %// P3: 104,370,000,000,000,000,000,000.000 %// // R: 1.0437E+21// #,000.000: 1,043,700,000,000,000,000,000.000// 0.###E-000: 1.044E021// 000,000,000,000.00###: 1,043,700,000,000,000,000,000.00// // Formatting of -1.0573E-05:// C: $0.00// C0: $0// C1: $0.0// C2: $0.00// C3: $0.000// // E: -1.057300E-005// E0: -1E-005// E1: -1.1E-005// E2: -1.06E-005// E3: -1.057E-005// // e: -1.057300e-005// e0: -1e-005// e1: -1.1e-005// e2: -1.06e-005// e3: -1.057e-005// // F: 0.00// F0: 0// F1: 0.0// F2: 0.00// F3: 0.000// // G: -1.0573E-05// G0: -1.0573E-05// G1: -1E-05// G2: -1.1E-05// G3: -1.06E-05// // N: 0.00// N0: 0// N1: 0.0// N2: 0.00// N3: 0.000// // P: 0.00 %// P0: 0 %// P1: 0.0 %// P2: 0.00 %// P3: -0.001 %// // R: -1.0573E-05// #,000.000: 000.000// 0.###E-000: -1.057E-005// 000,000,000,000.00###: -000,000,000,000.00001Double类型转String 类型出现精度丢失问题
C#中Double值用ToString()方法获取string
若Double数字位数超过16位就会造成精度缺失
建议用取整和取小数部分再合并的方式获取相对精确的string
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