将对象列表写入文件

Question

我有一个以下格式的班级推销员:

class salesman
{
    public string name, address, email;
    public int sales;
}

我有另一个用户输入姓名,地址,电子邮件和销售的课程.然后将此输入添加到列表中

List<salesman> salesmanList = new List<salesman>();

在用户根据需要向列表中输入尽可能多的推销员之后,他们可以选择将列表保存到他们选择的文件中(我可以将其限制为.xml或.txt(这更适合)).如何将此列表添加到文件中？如果用户希望稍后查看记录,则还需要将该文件重新读回列表.

Answer 1

像这样的东西会起作用.这使用二进制格式(最快加载)但相同的代码将适用于具有不同序列化程序的xml.

using System.IO;

    [Serializable]
    class salesman
    {
        public string name, address, email;
        public int sales;
    }

    class Program
    {
        static void Main(string[] args)
        {
            List<salesman> salesmanList = new List<salesman>();
            string dir = @"c:\temp";
            string serializationFile = Path.Combine(dir, "salesmen.bin");

            //serialize
            using (Stream stream = File.Open(serializationFile, FileMode.Create))
            {
                var bformatter = new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();

                bformatter.Serialize(stream, salesmanList);
            }

            //deserialize
            using (Stream stream = File.Open(serializationFile, FileMode.Open))
            {
                var bformatter = new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();

                List<salesman>  salesman = (List<salesman>)bformatter.Deserialize(stream);
            }
        }
    }

Answer 2

我刚写了一篇关于将对象数据保存到Binary,XML或Json的博客文章 ; 将对象或对象列表写入文件.以下是以各种格式执行此操作的功能.有关详细信息,请参阅我的博文.

二进制

/// <summary>
/// Writes the given object instance to a binary file.
/// <para>Object type (and all child types) must be decorated with the [Serializable] attribute.</para>
/// <para>To prevent a variable from being serialized, decorate it with the [NonSerialized] attribute; cannot be applied to properties.</para>
/// </summary>
/// <typeparam name="T">The type of object being written to the XML file.</typeparam>
/// <param name="filePath">The file path to write the object instance to.</param>
/// <param name="objectToWrite">The object instance to write to the XML file.</param>
/// <param name="append">If false the file will be overwritten if it already exists. If true the contents will be appended to the file.</param>
public static void WriteToBinaryFile<T>(string filePath, T objectToWrite, bool append = false)
{
    using (Stream stream = File.Open(filePath, append ? FileMode.Append : FileMode.Create))
    {
        var binaryFormatter = new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();
        binaryFormatter.Serialize(stream, objectToWrite);
    }
}

/// <summary>
/// Reads an object instance from a binary file.
/// </summary>
/// <typeparam name="T">The type of object to read from the XML.</typeparam>
/// <param name="filePath">The file path to read the object instance from.</param>
/// <returns>Returns a new instance of the object read from the binary file.</returns>
public static T ReadFromBinaryFile<T>(string filePath)
{
    using (Stream stream = File.Open(filePath, FileMode.Open))
    {
        var binaryFormatter = new System.Runtime.Serialization.Formatters.Binary.BinaryFormatter();
        return (T)binaryFormatter.Deserialize(stream);
    }
}

XML

需要System.Xml程序集包含在项目中.

/// <summary>
/// Writes the given object instance to an XML file.
/// <para>Only Public properties and variables will be written to the file. These can be any type though, even other classes.</para>
/// <para>If there are public properties/variables that you do not want written to the file, decorate them with the [XmlIgnore] attribute.</para>
/// <para>Object type must have a parameterless constructor.</para>
/// </summary>
/// <typeparam name="T">The type of object being written to the file.</typeparam>
/// <param name="filePath">The file path to write the object instance to.</param>
/// <param name="objectToWrite">The object instance to write to the file.</param>
/// <param name="append">If false the file will be overwritten if it already exists. If true the contents will be appended to the file.</param>
public static void WriteToXmlFile<T>(string filePath, T objectToWrite, bool append = false) where T : new()
{
    TextWriter writer = null;
    try
    {
        var serializer = new XmlSerializer(typeof(T));
        writer = new StreamWriter(filePath, append);
        serializer.Serialize(writer, objectToWrite);
    }
    finally
    {
        if (writer != null)
            writer.Close();
    }
}

/// <summary>
/// Reads an object instance from an XML file.
/// <para>Object type must have a parameterless constructor.</para>
/// </summary>
/// <typeparam name="T">The type of object to read from the file.</typeparam>
/// <param name="filePath">The file path to read the object instance from.</param>
/// <returns>Returns a new instance of the object read from the XML file.</returns>
public static T ReadFromXmlFile<T>(string filePath) where T : new()
{
    TextReader reader = null;
    try
    {
        var serializer = new XmlSerializer(typeof(T));
        reader = new StreamReader(filePath);
        return (T)serializer.Deserialize(reader);
    }
    finally
    {
        if (reader != null)
            reader.Close();
    }
}

JSON

您必须包含对Newtonsoft.Json程序集的引用,该程序集可以从Json.NET NuGet Package获得.

/// <summary>
/// Writes the given object instance to a Json file.
/// <para>Object type must have a parameterless constructor.</para>
/// <para>Only Public properties and variables will be written to the file. These can be any type though, even other classes.</para>
/// <para>If there are public properties/variables that you do not want written to the file, decorate them with the [JsonIgnore] attribute.</para>
/// </summary>
/// <typeparam name="T">The type of object being written to the file.</typeparam>
/// <param name="filePath">The file path to write the object instance to.</param>
/// <param name="objectToWrite">The object instance to write to the file.</param>
/// <param name="append">If false the file will be overwritten if it already exists. If true the contents will be appended to the file.</param>
public static void WriteToJsonFile<T>(string filePath, T objectToWrite, bool append = false) where T : new()
{
    TextWriter writer = null;
    try
    {
        var contentsToWriteToFile = JsonConvert.SerializeObject(objectToWrite);
        writer = new StreamWriter(filePath, append);
        writer.Write(contentsToWriteToFile);
    }
    finally
    {
        if (writer != null)
            writer.Close();
    }
}

/// <summary>
/// Reads an object instance from an Json file.
/// <para>Object type must have a parameterless constructor.</para>
/// </summary>
/// <typeparam name="T">The type of object to read from the file.</typeparam>
/// <param name="filePath">The file path to read the object instance from.</param>
/// <returns>Returns a new instance of the object read from the Json file.</returns>
public static T ReadFromJsonFile<T>(string filePath) where T : new()
{
    TextReader reader = null;
    try
    {
        reader = new StreamReader(filePath);
        var fileContents = reader.ReadToEnd();
        return JsonConvert.DeserializeObject<T>(fileContents);
    }
    finally
    {
        if (reader != null)
            reader.Close();
    }
}

例

// Write the list of salesman objects to file.
WriteToXmlFile<List<salesman>>("C:\salesmen.txt", salesmanList);

// Read the list of salesman objects from the file back into a variable.
List<salesman> salesmanList = ReadFromXmlFile<List<salesman>>("C:\salesmen.txt");