c#中最简单的从查询中填充类的方法

本文关键字：方法 填充 最简单 查询 | 更新日期: 2023-09-27 18:13:55

我想从查询填充一个类。这是一个示例类:

private class TVChannelObject
{
    public string number { get; set; }
    public string title { get; set; }
    public string favoriteChannel { get; set; }
    public string description { get; set; }
    public string packageid { get; set; }
    public string format { get; set; }
}

如何从数据库查询中填充这个类?是否有任何方法可以自动做到这一点，只要表列名与类属性相同?

c#中最简单的从查询中填充类的方法

正如其他人建议的那样，ORM是最好的方法。但是，您可以使用反射来实现此功能:

using System.Reflection;
void Main()
{
    var connectionString = "...";
    var records = new Query(connectionString).SqlQuery<TVChannel>("select top 10 * from TVChannel");
}
private class TVChannel
{
    public string number { get; set; }
    public string title { get; set; }
    public string favoriteChannel { get; set; }
    public string description { get; set; }
    public string packageid { get; set; }
    public string format { get; set; }
}
public class Query
{
    private readonly string _connectionString;
    public Query(string connectionString)
    {
        _connectionString = connectionString;
    }
    public List<T> SqlQuery<T>(string query)
    {
        var result = new List<T>();
        using (var connection = new SqlConnection(_connectionString))
        {
            connection.Open();
            using (var command = connection.CreateCommand())
            {
                command.CommandText = query;
                using (var reader = command.ExecuteReader())
                {
                    var columns = Enumerable.Range(0, reader.FieldCount).Select(reader.GetName).ToArray();
                    var properties = typeof(T).GetProperties();
                    while (reader.Read())
                    {
                        var data = new object[reader.FieldCount];
                        reader.GetValues(data);
                        var instance = (T)Activator.CreateInstance(typeof(T));
                        for (var i = 0; i < data.Length; ++i)
                        {
                            if (data[i] == DBNull.Value)
                            {
                                data[i] = null;
                            }
                            var property = properties.SingleOrDefault(x => x.Name.Equals(columns[i], StringComparison.InvariantCultureIgnoreCase));
                            if (property != null)
                            {
                                property.SetValue(instance, Convert.ChangeType(data[i], property.PropertyType));
                            }
                        }
                        result.Add(instance);
                    }
                }
            }
        }
        return result;
    }
}

您可以在c#中使用Linq to SQL。使用Linq，你可以很容易地用c#类映射你的表，然后用几行代码查询或填充它们。

查看此链接:用Linq插入行到SQL

编辑:

您需要做的第一件事是将类映射到数据库表。像这样:

[Table(Name = "tvchannel")] // Here you put the name of the table in your database.
private class TVChannelObject
{
    Column(Name = "number", IsPrimaryKey = true)] // Here, number is the name of the column in the database and it is the primary key of the table.
    public string number { get; set; }
    [Column(Name = "title", CanBeNull = true)] // If the field is nullable, then you can set it on CanBeNull property.
    public string title { get; set; }
    [Column(Name = "channelFavorite", CanBeNull = true)] // Note that you can have a field in the table with a different name than the property in your class.
    public string favoriteChannel { get; set; }
    [Column(Name = "desc", CanBeNull = true)]
    public string description { get; set; }
    [Column(Name = "package", CanBeNull = false)]
    public string packageid { get; set; }
    [Column(Name = "format", CanBeNull = false)]
    public string format { get; set; }
}

在将数据库映射为表的相应字段之后，现在可以在类中构建一个方法来插入一行:

public void InsertTvChannel()
{
    // DataContext takes a connection string. 
    string connString = "Data Source=SomeServer;Initial Catalog=SomeDB;User ID=joe;Password=swordfish" //example
    DataContext db = new DataContext(connString);
    // Create a new object tv channel to insert
    TVChannelObject channel = new TVChannelObject();
    channel.number = 1;
    channel.title = "Some title";
    channel.favoriteChannel = "some channel";
    channel.description = "some description";
    channel.packageid = "the package id";
    channel.format = "the format";
    // Now that you have the object for the new channel, let's insert it:
    db.TVChannelObjects.InsertOnSubmit(channel); //this just adds to a collection. It is a prepare to insert.
    // Submit the change to the database.
    try
    {
         db.SubmitChanges();
    }
    catch (Exception e)
    {
         Console.WriteLine(e);
        // If you face errors, you can handle it with some code here.
        // ...
        // Try again.
        db.SubmitChanges();
    }
}

这段代码应该可以工作，只需要做一些调整。现在您有了一个使用Linq映射插入的示例。

使用类似ORM的实体框架。为方便起见，请点击以下链接

www.codeproject.com/Articles/739164/Entity-Framework-Tutorial-for-Beginners

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