我收到一个字符串，其中包含系统中当前运行的 sw 版本。
只有当系统运行在某个 sw 版本或更高版本上时，我才想做一些操作。
例如，如果系统运行的是 sw 版本2.D或更高版本 ( 2.E, ..) 我会进行一些操作。如果系统运行较低的 sw 版本 ( 2.C, ..)，那么我不这样做。
如何对字符串进行这种比较？
问问题
2198 次
2 回答
0
有很多方法可以做到这一点，但如果你知道字符串的形式是 xy 甚至 xyz.. 那么我建议使用自定义 StringComparer：
using System;
using System.Linq;
using Microsoft.VisualStudio.TestTools.UnitTesting;
namespace StingComparisons
{
[TestClass]
public class StringComparison
{
[TestMethod]
public void TestMethod1()
{
var a = "2.E";
var b = "2.F";
var c = "2.C";
var d = "1.F";
var e = "3.A";
StringComparer comp = new MyStringComparer();
Assert.IsTrue(b.IsSameOrAfter(a, comp));
Assert.IsFalse(c.IsSameOrAfter(a, comp));
Assert.IsFalse(d.IsSameOrAfter(a, comp));
Assert.IsTrue(e.IsSameOrAfter(a, comp));
Assert.IsTrue(a.IsSameOrAfter(a, comp));
}
[TestMethod]
public void TestMethod2()
{
var a = "2.E.1";
var b = "2.E";
var c = "2.E.2";
var d = "2.F";
var e = "2.D.3";
var f = "3.A";
StringComparer comp = new MyStringComparer();
Assert.IsFalse(b.DotDelimitedIsSameOrAfter(a));
Assert.IsTrue(c.DotDelimitedIsSameOrAfter(a));
Assert.IsTrue(d.DotDelimitedIsSameOrAfter(a));
Assert.IsFalse(e.DotDelimitedIsSameOrAfter(a));
Assert.IsTrue(f.DotDelimitedIsSameOrAfter(a));
Assert.IsTrue(a.DotDelimitedIsSameOrAfter(a));
}
}
public static class stringExtensions
{
public static bool DotDelimitedIsSameOrAfter(this string a, string b)
{
return a.IsSameOrAfter(b, new MyStringComparer());
}
public static bool IsSameOrAfter(this string a, string b, StringComparer comp)
{
return comp.Compare(a, b) <= 0;
}
}
public class MyStringComparer : StringComparer
{
public override int Compare(string x, string y)
{
var partsX = x.Split('.');
var partsY = y.Split('.');
for (int i = 0; i < partsY.Length; i++)
{
if (partsX.Length <= i)
return 1;
var partComp = partsY[i].CompareTo(partsX[i]);
if (partComp != 0)
return partComp;
}
return 0;
}
public override bool Equals(string x, string y)
{
return x.Equals(y);
}
public override int GetHashCode(string obj)
{
return obj.GetHashCode();
}
}
}
我将调用包装在扩展方法中，纯粹是为了使其更具可读性。
于 2013-11-13T12:54:55.577 回答
0
由于我只需要那个（以及更多），我编写了以下比较器来比较两个字母数字版本字符串：
/// <summary>
/// Compares two alphanumeric version numbers.
/// </summary>
public class AlphanumericVersionComparer : IComparer<string>
{
/// <summary>
/// Compares two alphanumeric version numbers and returns a value
/// indicating whether one is less than, equal to, or greater than the other.
/// </summary>
/// <param name="x">The first alphanumeric version number to compare.</param>
/// <param name="y">The second alphanumeric version number to compare.</param>
/// <returns>A signed integer that indicates the relative values of x and y.</returns>
public int Compare(string x, string y)
{
// Validate parameters
if (x == null) throw new ArgumentNullException("x");
if (y == null) throw new ArgumentNullException("y");
// Test for equality
if (x == y)
return 0;
// Split the different parts of the number
string[] xParts = x.Split('.');
string[] yParts = y.Split('.');
// Compare each parts
AlphanumericComparer alphaNumComparer = new AlphanumericComparer();
for (int i = 0, n = Math.Max(xParts.Length, yParts.Length); i < n; i++)
{
// If the part at index i is not in y => x is greater
if (i >= yParts.Length)
return 1;
// If the part at index i is not in x => y is greater
if (i >= xParts.Length)
return -1;
// Compare the two alphanumerical numbers
int result = alphaNumComparer.Compare(xParts[i], yParts[i]);
if (result != 0)
{
return result;
}
}
// The two numbers are equal (really??? I thought we tested for equality already!)
System.Diagnostics.Debug.Fail("Not supposed to reach this code...");
return 0;
}
}
/// <summary>
/// Compares two alphanumeric strings.
/// </summary>
/// <remarks>See http://snipd.net/alphanumericnatural-sorting-in-c-using-icomparer </remarks>
public class AlphanumericComparer : IComparer<string>
{
/// <summary>
/// Compares two alphanumerics and returns a value
/// indicating whether one is less than, equal to, or greater than the other.
/// </summary>
/// <param name="x">The first alphanumeric to compare.</param>
/// <param name="y">The second alphanumeric to compare.</param>
/// <returns>A signed integer that indicates the relative values of x and y.</returns>
public int Compare(string x, string y)
{
int len1 = x.Length;
int len2 = y.Length;
int marker1 = 0;
int marker2 = 0;
// Walk through two the strings with two markers.
while (marker1 < len1 && marker2 < len2)
{
char ch1 = x[marker1];
char ch2 = y[marker2];
// Some buffers we can build up characters in for each chunk.
char[] space1 = new char[len1];
int loc1 = 0;
char[] space2 = new char[len2];
int loc2 = 0;
// Walk through all following characters that are digits or
// characters in BOTH strings starting at the appropriate marker.
// Collect char arrays.
do
{
space1[loc1++] = ch1;
marker1++;
if (marker1 < len1)
{
ch1 = x[marker1];
}
else
{
break;
}
} while (char.IsDigit(ch1) == char.IsDigit(space1[0]));
do
{
space2[loc2++] = ch2;
marker2++;
if (marker2 < len2)
{
ch2 = y[marker2];
}
else
{
break;
}
} while (char.IsDigit(ch2) == char.IsDigit(space2[0]));
// If we have collected numbers, compare them numerically.
// Otherwise, if we have strings, compare them alphabetically.
string str1 = new string(space1);
string str2 = new string(space2);
int result;
if (char.IsDigit(space1[0]) && char.IsDigit(space2[0]))
{
int thisNumericChunk = int.Parse(str1);
int thatNumericChunk = int.Parse(str2);
result = thisNumericChunk.CompareTo(thatNumericChunk);
}
else
{
result = str1.CompareTo(str2);
}
if (result != 0)
{
return result;
}
}
return len1 - len2;
}
}
你可以在这里玩小提琴：https ://dotnetfiddle.net/28iius 。
所有学分归于http://snipd.net/alphanumericnatural-sorting-in-c-using-icomparer用于字母数字比较。
于 2016-02-12T10:30:28.217 回答