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C#實(shí)現(xiàn)將字符串轉(zhuǎn)化為日期格式的方法詳解

 更新時(shí)間：2024年01月29日 10:04:14   作者：wenchm  
這篇文章主要為大家詳細(xì)介紹了C#如何使用DateTime結(jié)構(gòu)的ParseExact方法和Parse方法分別將字符串轉(zhuǎn)化為日期格式,有需要的小伙伴可以了解一下

在程序設(shè)計(jì)過程中，經(jīng)常需要顯示系統(tǒng)日期，使用DateTime結(jié)構(gòu)的Now屬性可以獲取系統(tǒng)的日期信息，此時(shí)調(diào)用ToString方法，將會(huì)返回日期的字符串表示，那么，怎樣將字符串轉(zhuǎn)換為日期格式呢?ParseExact方法可以輕松地實(shí)現(xiàn)此功能。

一、涉及到的知識(shí)點(diǎn) 

1.ParseExact(String, String, IFormatProvider)

將日期和時(shí)間的指定字符串表示形式轉(zhuǎn)換為其等效的 DateTime。 字符串表示形式的格式必須與指定的格式完全匹配，否則會(huì)引發(fā)異常。

publie static DateTime ParseExact(string s,string format,IFormatProvider provider)

參數(shù)

s    String 包含要轉(zhuǎn)換的日期和時(shí)間的字符串。

format    String 用于定義所需的 s 格式的格式說明符。 有關(guān)詳細(xì)信息，請參閱“備注”部分。

provider    IFormatProvider 一個(gè)對(duì)象，提供有關(guān) s 的區(qū)域性特定格式信息。

返回

DateTime 一個(gè)對(duì)象，它等效于 s 中包含的日期和時(shí)間，由 format 和 provider 指定。

ArgumentNullException

s 或 format 為 null。

FormatException

s 或 format 是一個(gè)空字符串。

或 -

s 不包含與 format 中指定的模式相對(duì)應(yīng)的日期和時(shí)間。

或 -

s 中的小時(shí)組件和 AM/PM 指示符不一致。

ParseExact方法中的參數(shù)說明如下表：

參    數(shù)描   述
 s字符串對(duì)象，表示包含要轉(zhuǎn)換的日期和時(shí)間的字符串
format字符串對(duì)象，表示s的預(yù)期格式
provide實(shí)現(xiàn)IFormatProvider接口的對(duì)象，表示用于提供有關(guān)s的區(qū)域性特定格式信息的IFormatProvider
DateTime方法返回DateTime對(duì)象，等效于由format和provider所指定的s中包含的日期和時(shí)間

2.DateTime.ToLongDateString 方法

將當(dāng)前 DateTime 對(duì)象的值轉(zhuǎn)換為其等效的長日期字符串表示形式。

public string ToLongDateString ();

返回

String 一個(gè)字符串，它包含當(dāng)前 DateTime 對(duì)象的長日期字符串表示形式。

// DateTime.ToLongDateString 方法
using System.Globalization;
 
namespace _067_3
{
    class Sample
    {
        public static void Main()
        {
            // 初始化 DateTime 對(duì)象
            Console.WriteLine("Initialize the DateTime object to Jan 28, 2024 22:23:15 PM.\n");
            DateTime datetime = new(2024, 1, 28, 22, 23, 15);
 
            // 當(dāng)前區(qū)域
            Console.WriteLine($"Current culture: \"{CultureInfo.CurrentCulture.Name}\"\n");
            var dtFormat = CultureInfo.CurrentCulture.DateTimeFormat;
 
            // Display the long date pattern and string.
            Console.WriteLine($"Long date pattern: \"{dtFormat.LongDatePattern}\"");
            Console.WriteLine($"Long date string:  \"{datetime.ToLongDateString()}\"\n");
 
            // Display the long time pattern and string.
            Console.WriteLine($"Long time pattern: \"{dtFormat.LongTimePattern}\"");
            Console.WriteLine($"Long time string:  \"{datetime.ToLongTimeString()}\"\n");
 
            // Display the short date pattern and string.
            Console.WriteLine($"Short date pattern: \"{dtFormat.ShortDatePattern}\"");
            Console.WriteLine($"Short date string:  \"{datetime.ToShortDateString()}\"\n");
 
            // Display the short time pattern and string.
            Console.WriteLine($"Short time pattern: \"{dtFormat.ShortTimePattern}\"");
            Console.WriteLine($"Short time string:  \"{datetime.ToShortTimeString()}\"\n");
        }
    }
}
// 運(yùn)行結(jié)果:
/*
Initialize the DateTime object to Jan 28, 2024 22:23:15 PM.
Current culture: "zh-CN"
Long date pattern: "yyyy-MM-dd"
Long date string:  "2024-01-28"
Long time pattern: "HH:mm:ss"
Long time string:  "22:23:15"
Short date pattern: "yyyy-MM-dd"
Short date string:  "2024-01-28"
Short time pattern: "H:mm"
Short time string:  "22:23"
 */

3.Parse(String)方法

使用當(dāng)前區(qū)域性的約定將日期和時(shí)間的字符串表示形式轉(zhuǎn)換為其 DateTime 等效的表示形式。

public static DateTime Parse (string s);

參數(shù)

s    String  包含要轉(zhuǎn)換的日期和時(shí)間的字符串。 有關(guān)詳細(xì)信息，請參閱要分析的字符串。 

返回

DateTime 一個(gè)對(duì)象，它等效于 s 中包含的日期和時(shí)間。

例外

ArgumentNullException

s 為 null。

FormatException

s 不包含日期和時(shí)間的有效字符串表示形式。

二、實(shí)例1：ParseExact方法

1.源碼

// 使用ParseExact方法將字符串轉(zhuǎn)化為日期格式
namespace _067
{
    public partial class Form1 : Form
    {
        private GroupBox? groupBox1;
        private Button? button1;
        private Label? label3;
        private Label? label2;
        private Label? label1;
        private TextBox? textBox3;
        private TextBox? textBox2;
        private TextBox? textBox1;
 
        public Form1()
        {
            InitializeComponent();
            Load += Form1_Load;
        }
        private void Form1_Load(object? sender, EventArgs e)
        {
            // 
            // label3
            // 
            label3 = new Label
            {
                AutoSize = true,
                Location = new Point(285, 37),
                Name = "label3",
                Size = new Size(20, 17),
                TabIndex = 5,
                Text = "日"
            };
            // 
            // label2
            //         
            label2 = new Label
            {
                AutoSize = true,
                Location = new Point(203, 37),
                Name = "label2",
                Size = new Size(20, 17),
                TabIndex = 4,
                Text = "月"
            };
            // 
            // textBox2
            //          
            textBox2 = new TextBox
            {
                Location = new Point(147, 31),
                Name = "textBox2",
                Size = new Size(50, 23),
                TabIndex = 1
            };
            // 
            // textBox1
            //           
            textBox1 = new TextBox
            {
                Location = new Point(35, 31),
                Name = "textBox1",
                Size = new Size(80, 23),
                TabIndex = 0
            };
            // 
            // label1
            //  
            label1 = new Label
            {
                AutoSize = true,
                Location = new Point(121, 37),
                Name = "label1",
                Size = new Size(20, 17),
                TabIndex = 3,
                Text = "年"
            };
            // 
            // textBox3
            //          
            textBox3 = new TextBox
            {
                Location = new Point(229, 31),
                Name = "textBox3",
                Size = new Size(50, 23),
                TabIndex = 2
            };
            // 
            // button1
            //           
            button1 = new Button
            {
                Location = new Point(141, 81),
                Name = "button1",
                Size = new Size(75, 23),
                TabIndex = 0,
                Text = "轉(zhuǎn)為日期",
                UseVisualStyleBackColor = true
            };
            button1.Click += Button1_Click;
            // 
            // groupBox1
            // 
            groupBox1 = new GroupBox
            {
                Location = new Point(12, 12),
                Name = "groupBox1",
                Size = new Size(340, 63),
                TabIndex = 0,
                TabStop = false,
                Text = "輸入日期字符串"
            };
            groupBox1.Controls.Add(label3);
            groupBox1.Controls.Add(label2);
            groupBox1.Controls.Add(textBox2);
            groupBox1.Controls.Add(textBox1);
            groupBox1.Controls.Add(label1);
            groupBox1.Controls.Add(textBox3);
            groupBox1.SuspendLayout();
 
            // 
            // Form1
            // 
            AutoScaleDimensions = new SizeF(7F, 17F);
            AutoScaleMode = AutoScaleMode.Font;
            ClientSize = new Size(364, 116);
            Controls.Add(button1);
            Controls.Add(groupBox1);
            Name = "Form1";
            StartPosition = FormStartPosition.CenterScreen;
            Text = "用ParseExact方法將字符串轉(zhuǎn)為日期";
            groupBox1.ResumeLayout(false);
            groupBox1.PerformLayout();
        }
        /// <summary>
        /// 得到日期字符串
        /// 將字符串轉(zhuǎn)換為日期格式
        /// </summary>
        private void Button1_Click(object? sender, EventArgs e)
        {
            string str = string.Format("{0}/{1}/{2}",textBox1!.Text, textBox2!.Text, textBox3!.Text);
            DateTime datetime = DateTime.ParseExact(str, "yyyy/MM/dd", null); 
            MessageBox.Show("輸入的日期為： "+ datetime.ToLongDateString(), "提示！");
        }
    }
}

2.生成效果 

3.示例2

// ParseExact 方法
using System.Globalization;
 
namespace _067_1
{
    public class Example
    {
        public static void Main()
        {
            string dateString, format;
            DateTime result;
            CultureInfo provider = CultureInfo.InvariantCulture;
 
            // 解析不變區(qū)域的日期值
            dateString = "01/28/2024";
            format = "d";
            try
            {
                result = DateTime.ParseExact(dateString, format, provider);
                Console.WriteLine("{0} converts to {1}.", dateString, result.ToString());
            }
            catch (FormatException)
            {
                Console.WriteLine("{0} is not in the correct format.", dateString);
            }
 
            // 使用“d”格式解析月份中不帶前導(dǎo)零的日期值
            // 不變區(qū)域的標(biāo)準(zhǔn)短日期模式需要兩位數(shù)的月份
            // 否則拋出 FormatException
            dateString = "1/28/2024";
            try
            {
                result = DateTime.ParseExact(dateString, format, provider);
                Console.WriteLine("{0} converts to {1}.", dateString, result.ToString());
            }
            catch (FormatException)
            {
                Console.WriteLine("{0} is not in the correct format.", dateString);
            }
 
            // 使用自定義說明符轉(zhuǎn)換日期和時(shí)間。
            dateString = "Sun 28 Jan 2024 8:30 AM -06:00";
            format = "ddd dd MMM yyyy h:mm tt zzz";
            try
            {
                result = DateTime.ParseExact(dateString, format, provider);
                Console.WriteLine("{0} converts to {1}.", dateString, result.ToString());
            }
            catch (FormatException)
            {
                Console.WriteLine("{0} is not in the correct format.", dateString);
            }
 
            // 轉(zhuǎn)換帶偏移量的日期和時(shí)間，但沒有分鐘的偏移量時(shí)，
            // “zzz”說明符需要以小時(shí)為單位前導(dǎo)零,
            // 否則拋出 FormatException
            // 這里有兩處錯(cuò)誤：1日不是Sun和06:00
            dateString = "Sun 01 Jan 2024 8:30 AM -06";
            try
            {
                result = DateTime.ParseExact(dateString, format, provider);
                Console.WriteLine("{0} converts to {1}.", dateString, result.ToString());
            }
            catch (FormatException)
            {
                Console.WriteLine("{0} is not in the correct format.", dateString);
            }
 
            dateString = "28/01/2024 08:45";
            format = "g";
            provider = new CultureInfo("fr-FR");
            try
            {
                result = DateTime.ParseExact(dateString, format, provider);
                Console.WriteLine("{0} converts to {1}.", dateString, result.ToString());
            }
            catch (FormatException)
            {
                Console.WriteLine("{0} is not in the correct format.", dateString);
            }
 
            // 使用法語（法國）和不變區(qū)域轉(zhuǎn)換包含秒和毫秒的日期
            dateString = "28/01/2024 08:30:15.006542";
            format = "dd/MM/yyyy HH:mm:ss.ffffff";
            try
            {
                result = DateTime.ParseExact(dateString, format, provider);
                Console.WriteLine("{0} converts to {1}.", dateString, result.ToString());
            }
            catch (FormatException)
            {
                Console.WriteLine("{0} is not in the correct format.", dateString);
            }
        }
    }
}
// 運(yùn)行結(jié)果：
/*
01/28/2024 converts to 2024-01-28 00:00:00.
1/28/2024 is not in the correct format.
Sun 28 Jan 2024 8:30 AM -06:00 converts to 2024-01-28 22:30:00.
Sun 01 Jan 2024 8:30 AM -06 is not in the correct format.
28/01/2024 08:45 converts to 2024-01-28 08:45:00.
28/01/2024 08:30:15.006542 converts to 2024-01-28 08:30:15.
 */

三、實(shí)例2：Parse方法

// 以Parse(String)方法轉(zhuǎn)換多個(gè)日期和時(shí)間值的字符串表示形式
using System.Globalization;
 
namespace _067_2
{
    public class DateTimeParser
    {
        public static void Main()
        {
            DateTime dateValue;
            string datetime = "1/28/2024 12:15:12 PM";
            try
            {
                dateValue = DateTime.Parse(datetime);
                Console.WriteLine("'{0}' converted to {1}.", datetime, dateValue);
            }
            catch (FormatException)
            {
                Console.WriteLine("Unable to convert '{0}'.", datetime);
            }
 
            // Reverse month and day to conform to the fr-FR culture.
            // The date is February 16, 2008, 12 hours, 15 minutes and 12 seconds.
            datetime = "28/01/2024 12:35:20";   //正確順序01/28/2024
            try
            {
                dateValue = DateTime.Parse(datetime);
                Console.WriteLine("'{0}' converted to {1}.", datetime, dateValue);
            }
            catch (FormatException)
            {
                Console.WriteLine("Unable to convert '{0}'.", datetime);
            }
 
            // formatted according to conventions of zh-HK Chinese - Hong Kong SAR culture.
            // 沒有zh-CN Chinese - China和zh-CHS Chinese (Simplified) , Neutral
            try
            {
                dateValue = DateTime.Parse(datetime, new CultureInfo("zh-HK", false));
                Console.WriteLine("'{0}' converted to {1}.", datetime, dateValue);
            }
            catch (FormatException)
            {
                Console.WriteLine("Unable to convert '{0}'.", datetime);
            }
 
            // 轉(zhuǎn)換字符串型日期，不包含時(shí)間
            datetime = "1/28/2024";
            try
            {
                dateValue = DateTime.Parse(datetime);
                Console.WriteLine("'{0}' converted to {1}.", datetime, dateValue);
            }
            catch (FormatException)
            {
                Console.WriteLine("Unable to convert '{0}'.", datetime);
            }
        }
    }
}
//運(yùn)行結(jié)果：
/*
'1/28/2024 12:15:12 PM' converted to 2024-01-28 12:15:12.
Unable to convert '28/01/2024 12:35:20'.
'28/01/2024 12:35:20' converted to 2024-01-28 12:35:20.
'1/28/2024' converted to 2024-01-28 00:00:00.
 */

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