FastDev介绍系列之[数据类型转换类]

这是FastDev.Core程序集中的一个类Converters, 用于数据类型转换.
使用方法: Converters.ChangeType<T>(toChangeObject) 或 toChangeObject.ChangeType<T>()
测试如下:

using System;
using System.Text;
using System.Collections.Generic;
using System.Linq;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Runtime.Remoting.Messaging;
using System.Threading;

namespace FastDev.Core.Test
{
    /**//// <summary>
    /// 测试枚举
    /// </summary>
    public enum EnumType : int
    {
        First,
        Second
    }

    [TestClass]
    public class ConvertersTest
    {
        [TestMethod()]
        public void TestChangeType()
        {
            //BaseType Change
            ChangeTypeTestHelper<string>(1, "1");
            ChangeTypeTestHelper<bool>("True", true);

            //T -> Nullable<T>, Not Null
            ChangeTypeTestHelper<int?>(1, new Nullable<int>(1));

            //Nullable<T> -> T, Not Null
            ChangeTypeTestHelper<int>(new Nullable<int>(1), 1);

            //Null -> Nullable<T>
            int? intNullable = null;
            ChangeTypeTestHelper<int?>(null, intNullable);
            ChangeTypeTestHelper<int?>(string.Empty, null);

            //Nullable<T> -> Null
            ChangeTypeTestHelper<object>(intNullable, null);
            ChangeTypeTestHelper<int>(intNullable, 0);

            //多重转换
            ChangeTypeTestHelper<DateTime?>("2007-12-12", new DateTime?(new DateTime(2007, 12, 12)));

            //Ojbect -> Enum
            ChangeTypeTestHelper<EnumType>("1", EnumType.Second);
            ChangeTypeTestHelper<EnumType>((object)"1", EnumType.Second);
            ChangeTypeTestHelper<EnumType>((object)1, EnumType.Second);
        }

        public void ChangeTypeTestHelper<T>(object toChangeObject, T expected)
        {
            Assert.AreEqual(expected, Converters.ChangeType<T>(toChangeObject));
        }

        [TestMethod]
        public void TestChangeEnumerableType()
        {
            string[] strArr = { "1", "2" };
            List<long> longArr = strArr.ChangeEnumerableType<long>();
            Assert.AreEqual(2, longArr.Count);
            Assert.AreEqual(1, longArr[0]);
            Assert.AreEqual(2, longArr[1]);

            object[] objArr = { EnumType.First, EnumType.Second };
            List<EnumType> enumArr = objArr.ChangeEnumerableType<EnumType>();
            Assert.AreEqual(EnumType.First, enumArr[0]);
        }
    }
}

源代码:

using System;
using System.Text;
using System.Collections.Generic;
using System.Linq;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Runtime.Remoting.Messaging;
using System.Threading;

namespace FastDev.Core.Test
{
    /**//// <summary>
    /// 测试枚举
    /// </summary>
    public enum EnumType : byte
    {
        First,
        Second
    }

    [TestClass]
    public class ConvertersTest
    {
        [TestMethod()]
        public void TestChangeType()
        {
            //BaseType Change
            ChangeTypeTestHelper<string>(1, "1");
            ChangeTypeTestHelper<bool>("True", true);

            //T -> Nullable<T>, Not Null
            ChangeTypeTestHelper<int?>(1, new Nullable<int>(1));

            //Nullable<T> -> T, Not Null
            ChangeTypeTestHelper<int>(new Nullable<int>(1), 1);

            //Null -> Nullable<T>
            int? intNullable = null;
            ChangeTypeTestHelper<int?>(null, intNullable);
            ChangeTypeTestHelper<int?>(string.Empty, null);

            //Nullable<T> -> Null
            ChangeTypeTestHelper<object>(intNullable, null);
            ChangeTypeTestHelper<int>(intNullable, 0);

            //多重转换
            ChangeTypeTestHelper<DateTime?>("2007-12-12", new DateTime?(new DateTime(2007, 12, 12)));

            //Ojbect -> Enum
            ChangeTypeTestHelper<EnumType>("1", EnumType.Second);
            ChangeTypeTestHelper<EnumType>((object)"1", EnumType.Second);
            ChangeTypeTestHelper<EnumType>((object)1, EnumType.Second);
        }

        public void ChangeTypeTestHelper<T>(object toChangeObject, T expected)
        {
            Assert.AreEqual(expected, Converters.ChangeType<T>(toChangeObject));
        }

        [TestMethod]
        public void TestChangeEnumerableType()
        {
            string[] strArr = { "1", "2" };
            List<long> longArr = strArr.ChangeEnumerableType<long>();
            
            Assert.AreEqual(2, longArr.Count);
            Assert.AreEqual(1, longArr[0]);
            Assert.AreEqual(2, longArr[1]);
        }
    }

using System;
using System.Collections.Generic;
using System.Text;
using System.ComponentModel;
using System.Linq;
using System.Collections;

namespace FastDev.Core
{
    /**//// <summary>
    /// 类型转换
    /// </summary>
    public static class Converters
    {
        /**//// <summary>
        /// 强制类型转换, 如果为枚举, 则按枚举值计算
        /// </summary>
        /// <typeparam name="T">要转换成的类型</typeparam>
        /// <param name="toChangeObject">转换目标</param>
        public static T ChangeType<T>(object toChangeObject)
        {
            Type conversionType = typeof(T);

            if (Convert.IsDBNull(toChangeObject) || toChangeObject == null || toChangeObject.ToString() == "")
            {
                return default(T);
            }

            // 只支持值的转换, 不支持Enum字面的转换
            if (conversionType.IsEnum) // Object -> Enum = Object -> UnderlyingType -> Enum
            {
                toChangeObject = Convert.ChangeType(toChangeObject, Enum.GetUnderlyingType(conversionType));
                return (T)toChangeObject;
            }

            //如果转换类型为Nullable<T>, 就将转换类型变成T
            if (conversionType.IsGenericType && conversionType.GetGenericTypeDefinition() == (typeof(Nullable<>)))
            {
                NullableConverter nullableConverter = new NullableConverter(conversionType);
                conversionType = nullableConverter.UnderlyingType;
            }

            return (T)Convert.ChangeType(toChangeObject, conversionType);
        }

        /**//// <summary>
        /// 数组的强制类型转换, 如果为枚举, 则按枚举值计算
        /// </summary>
        /// <typeparam name="T">要转换成的类型</typeparam>
        /// <param name="toChangeObject">转换目标</param>
        public static List<T> ChangeEnumerableType<T>(IEnumerable enumerable)
        {
            List<T> result = new List<T>();
            foreach (object item in enumerable)
            {
                result.Add(item.ChangeType<T>());
            }

            return result;
        }
    }
}

扩展方法:

using System;
using System.Collections.Generic;
using System.Text;
using System.ComponentModel;
using System.Collections;

namespace FastDev.Core
{
    public static class ConvertersExtensions
    {
        public static T ChangeType<T>(this object toChangeObject)
        {
            return Converters.ChangeType<T>(toChangeObject);
        }

        public static List<T> ChangeEnumerableType<T>(this IEnumerable enumerable)
        {
            return Converters.ChangeEnumerableType<T>(enumerable);
        }
    }
}