BitConverter.ToDouble()方法用于返回双精度浮点数，该浮点数从字节数组中指定位置的八个字节转换而来。
句法：
public static double ToDouble (byte[] value, int startIndex);参数：
value: It is an array of bytes.
startIndex: It is the starting position within the value.
返回值：该方法返回一个双精度浮点数，该数由从startIndex开始的八个字节组成。
例外情况：
- ArgumentException：如果startIndex大于或等于值的长度减去7，并且小于或等于值的长度减去1。
- ArgumentNullException：如果该值为null。
- ArgumentOutOfRangeException：如果startIndex小于零或大于值的长度减去1。
下面的程序说明了BitConverter.ToDouble(Byte []，Int32)方法的用法：
范例1：
// C# program to demonstrate
// BitConverter.ToDouble(Byte[], Int32)
// Method
using System;
class GFG {
// Main Method
public static void Main()
{
try {
// Define an array of byte values.
byte[] bytes = {0,0,1,2,7,126,78,55,
255,78,45,198,200,1,
1,1,1,255,255,2,4,4,
77,77,77,77,77,0,1};
// Display the values of the myArr.
Console.WriteLine("Initial Array: ");
// calling the PrintIndexAndValues()
// method to print
PrintIndexAndValues(bytes);
// print char value
Console.WriteLine("index Array elements "+
" double values");
Console.WriteLine();
// getting double value and Display it
for (int index = 0; index < bytes.Length - 7;
index = index + 8) {
double values = BitConverter.ToDouble(bytes, index);
Console.WriteLine(" {0} {1} {2}",
index, BitConverter.ToString(bytes,
index, 8), values);
}
}
catch (ArgumentNullException e) {
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
catch (ArgumentOutOfRangeException e) {
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
catch (ArgumentException e) {
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
}
// Defining the method
// PrintIndexAndValues
public static void PrintIndexAndValues(byte[] myArr)
{
int count = 0;
for (int i = 0; i < myArr.Length; i++) {
if (count == 18) {
Console.WriteLine();
Console.Write("{0} ", myArr[i]);
count = 0;
}
else {
Console.Write("{0} ", myArr[i]);
count++;
}
}
Console.WriteLine();
Console.WriteLine();
}
}
输出：
Initial Array:
0 0 1 2 7 126 78 55 255 78 45 198 200 1 1 1 1 255
255 2 4 4 77 77 77 77 77 0 1
index Array elements double values
0 00-00-01-02-07-7E-4E-37 2.73464354303054E-42
8 FF-4E-2D-C6-C8-01-01-01 7.74999325882041E-304
16 01-FF-FF-02-04-04-4D-4D 2.38727219494443E+64
示例2：对于ArgumentException
// C# program to demonstrate
// BitConverter.ToDouble(Byte[], Int32)
// Method
using System;
class GFG {
// Main Method
public static void Main()
{
try {
// Define an array of byte values.
byte[] bytes = {0,0,1,2,7,126,78,55,
255,78,45,198,200,1,
1,1,1,255,255,2,4,4,
77,77,77,77,77,0,1,
0,0,1,2,7,126,78,55,
255,78,45,198,200,1,
1,1,1,255,255,2,4,4,
255,255,255,255,245,
245,245,245,245,245,
245,245,245,245,0,0,
0,0,0,0,0,0,6,5,6,56,
31,31,31,54,23,253,};
// Display the values of the myArr.
Console.WriteLine("Initial Array: ");
// calling the PrintIndexAndValues()
// method to print
PrintIndexAndValues(bytes);
// print char value
Console.WriteLine("index Array elements"+
" double values");
Console.WriteLine();
// getting double value and Display it
for (int index = 4; index < bytes.Length - 6;
index = index + 8) {
if (index == bytes.Length - 7) {
Console.WriteLine();
Console.WriteLine("startIndex is equal to"+
" the length of bytes minus 7");
double values = BitConverter.ToDouble(bytes, index);
Console.WriteLine(" {0} {1} {2}",
index, BitConverter.ToString(bytes,
index, 4), values);
}
else {
double values = BitConverter.ToDouble(bytes, index);
Console.WriteLine(" {0} {1} {2}",
index, BitConverter.ToString(bytes, index,
8), values);
}
}
}
catch (ArgumentNullException e) {
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
catch (ArgumentOutOfRangeException e) {
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
catch (ArgumentException e) {
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
}
// Defining the method
// PrintIndexAndValues
public static void PrintIndexAndValues(byte[] myArr)
{
int count = 0;
for (int i = 0; i < myArr.Length; i++) {
if (count == 18) {
Console.WriteLine();
Console.Write("{0} ", myArr[i]);
count = 0;
}
else {
Console.Write("{0} ", myArr[i]);
count++;
}
}
Console.WriteLine();
Console.WriteLine();
}
}
输出：
Initial Array:
0 0 1 2 7 126 78 55 255 78 45 198 200 1 1 1 1 255
255 2 4 4 77 77 77 77 77 0 1 0 0 1 2 7 126 78 55
255 78 45 198 200 1 1 1 1 255 255 2 4 4 255 255 255 255 245
245 245 245 245 245 245 245 245 245 0 0 0 0 0 0 0 0 6 5
6 56 31 31 31 54 23 253
index Array elements double values
4 07-7E-4E-37-FF-4E-2D-C6 -1.16103254047091E+30
12 C8-01-01-01-01-FF-FF-02 3.13113229681351E-294
20 04-04-4D-4D-4D-4D-4D-00 3.25995134720157E-307
28 01-00-00-01-02-07-7E-4E 1.29525825666467E+70
36 37-FF-4E-2D-C6-C8-01-01 8.10420695824091E-304
44 01-01-FF-FF-02-04-04-FF -6.86302832487538E+303
52 FF-FF-FF-F5-F5-F5-F5-F5 -1.68827860814431E+260
60 F5-F5-F5-F5-F5-00-00-00 5.21927749055768E-312
68 00-00-00-00-00-06-05-06 1.15818454395586E-279
startIndex is equal to the length of bytes minus 7
Exception Thrown: System.ArgumentException
示例3：对于ArgumentOutOfRangeException
// C# program to demonstrate
// BitConverter.ToDouble(Byte[], Int32)
// Method
using System;
class GFG {
// Main Method
public static void Main()
{
try {
// Define an array of byte values.
byte[] bytes = {0,0,1,2,7,126,78,55,
255,78,45,198,200,1,
1,1,1,255,255,2,4,4,
77,77,77,77,77,0,1,
0,0,1,2,7,126,78,55,
255,78,45,198,200,1,
1,1,1,255,255,2,4,4,
255,255,255,255,245,
245,245,245,245,245,
245,245,245,245,0,0,
0,0,0,0,0,0,6,5,6,56,
31,31,31,54,23,253,};
// Display the values of the myArr.
Console.WriteLine("Initial Array: ");
// calling the PrintIndexAndValues()
// method to print
PrintIndexAndValues(bytes);
// getting double value and Display it
Console.WriteLine("startIndex is less than zero");
double values = BitConverter.ToDouble(bytes, -1);
Console.WriteLine(" {0} {1} {2}", -1,
BitConverter.ToString(bytes, -1, 8),
values);
}
catch (ArgumentNullException e) {
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
catch (ArgumentOutOfRangeException e) {
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
catch (ArgumentException e) {
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
}
// Defining the method
// PrintIndexAndValues
public static void PrintIndexAndValues(byte[] myArr)
{
int count = 0;
for (int i = 0; i < myArr.Length; i++) {
if (count == 18) {
Console.WriteLine();
Console.Write("{0} ", myArr[i]);
count = 0;
}
else {
Console.Write("{0} ", myArr[i]);
count++;
}
}
Console.WriteLine();
Console.WriteLine();
}
}
输出：
Initial Array:
0 0 1 2 7 126 78 55 255 78 45 198 200 1 1 1 1 255
255 2 4 4 77 77 77 77 77 0 1 0 0 1 2 7 126 78 55
255 78 45 198 200 1 1 1 1 255 255 2 4 4 255 255 255 255 245
245 245 245 245 245 245 245 245 245 0 0 0 0 0 0 0 0 6 5
6 56 31 31 31 54 23 253
startIndex is less than zero
Exception Thrown: System.ArgumentOutOfRangeException
示例4：对于ArgumentNullException
// C# program to demonstrate
// BitConverter.ToDouble(Byte[], Int32)
// Method
using System;
class GFG {
// Main Method
public static void Main()
{
try {
// Define an array of byte values.
byte[] bytes = null;
// getting double value and Display it
Console.WriteLine("array bytes is null");
double values = BitConverter.ToDouble(bytes, 0);
Console.WriteLine(" {0} {1} {2}", 0,
BitConverter.ToString(bytes, 0, 8), values);
}
catch (ArgumentNullException e) {
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
catch (ArgumentOutOfRangeException e) {
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
catch (ArgumentException e) {
Console.Write("Exception Thrown: ");
Console.Write("{0}", e.GetType(), e.Message);
}
}
// Defining the method
// PrintIndexAndValues
public static void PrintIndexAndValues(byte[] myArr)
{
int count = 0;
for (int i = 0; i < myArr.Length; i++) {
if (count == 18) {
Console.WriteLine();
Console.Write("{0} ", myArr[i]);
count = 0;
}
else {
Console.Write("{0} ", myArr[i]);
count++;
}
}
Console.WriteLine();
Console.WriteLine();
}
}
输出：
array bytes is null
Exception Thrown: System.ArgumentNullException
参考：
- https://docs.microsoft.com/zh-cn/dotnet/api/system.bitconverter.todouble?view=netframework-4.7.2