检查类型最快的方法是什么? [英] What is the fastest way to check a type?

问题描述

我决定在一个函数中检查类型，而不是将函数重载100次或为不同类型创建100个不同的比较器.

Instead of overloading a function 100 times or creating 100 different Comparers for different types I've decided to check the type within one function.

例如，我正在使用默认比较器来比较2个对象内的一组类型(基元和字符串)的值.它包含以下代码:

For example I'm using a default comparer to compare values of a set of types (primitives and strings) within 2 objects. It contains the following code:

public class DefComparer : IComparer<object> {
    public int Compare(object a, object b) {
        .... // a = a.GetType().GetField(field).GetValue(a); - not important for the question but I'm just showing that a&b below are different references
        switch (a.GetType().Name) {
            case "Byte":
                if ((byte)a == (byte)b) return 0;
                else if ((byte)a > (byte)b) return 1;
                else return -1;
            case "UInt16":
                if ((ushort)a == (ushort)b) return 0;
                else if ((ushort)a > (ushort)b) return 1;
                else return -1;
            case "SByte":
                if ((sbyte)a == (sbyte)b) return 0;
                else if ((sbyte)a > (sbyte)b) return 1;
                else return -1;
            case "Int16":
                ...

这里我使用的是一个 switch 语句，据说它比 if / else 语句链要快.但是 a.GetType().Name 返回一个动态获取的字符串，并且此方法涉及字符串比较.在我看来，这听起来并不快.我需要比较器在技术上尽可能快，因为它将用于大量数据.

Here I'm using a switch statement that is said to be faster than a chain of if/else statements. But a.GetType().Name returns a string that is dynamically obtained and this method involves string comparisons. That doesn't sound particularly fast to me. I need the Comparer to be as fast as technically possible because It's going to be used on large collections of data.

问:有没有更快的方法来检查对象的类型(不涉及字符串比较)?最快的方法是什么?

推荐答案

好了.使用 TypeCode

        int a = 10;
        Type t = a.GetType();

        switch (Type.GetTypeCode(t))
        {
            case TypeCode.Boolean:
                break;
            case TypeCode.Byte:
                break;
            case TypeCode.Char:
                break;
            case TypeCode.DBNull:
                break;
            case TypeCode.DateTime:
                break;
            case TypeCode.Decimal:
                break;
            case TypeCode.Double:
                break;
            case TypeCode.Empty:
                break;
            case TypeCode.Int16:
                break;
            case TypeCode.Int32:
                break;
            case TypeCode.Int64:
                break;
            case TypeCode.Object:
                break;
            case TypeCode.SByte:
                break;
            case TypeCode.Single:
                break;
            case TypeCode.String:
                break;
            case TypeCode.UInt16:
                break;
            case TypeCode.UInt32:
                break;
            case TypeCode.UInt64:
                break;
            default:
                break;
        }

这支持所有原语.用于自定义对象在 TypeCode.Object 内写 else if 语句.

this supports all primitives. for Custom objects Write else if statements inside TypeCode.Object.

我希望这会有所帮助.

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