如何从C#中的SQL查询结果填充类? [英] How can I populate a class from the results of a SQL query in C#?

问题描述

我有一个像这样的课程:

I've got a class like this:

public class Product
{
    public int ProductId { get; private set; }
    public int SupplierId { get; private set; }

    public string Name { get; private set; }
    public decimal Price { get; private set; }
    public int Stock { get; private set; }
    public int PendingStock { get; private set; }
}

我可以这样从数据库中获取这些详细信息:

I can fetch those details from my database like this:

SELECT product_id, supplier_id, name, price, total_stock, pending_stock 
FROM products
WHERE product_id = ?

我不想手动通过DataSet或DataTable来设置值.

I don't want to have to manually run through a DataSet or DataTable to set the values.

我确定有一种使用某种绑定/映射机制填充类的方法，但是我唯一能找到的就是绑定到winforms组件或使用XAML.

I'm sure there's a way to populate the class using some kind of binding / mapping mechanism, but the only stuff I could find was for binding to winforms components or using XAML.

是否可以将某些属性应用于我的属性/类，以使该类从查询行中自动填充?

Is there some kind of attribute I can apply to my properties / class to have the class automatically populated from a query row?

推荐答案

我已决定提出另一个答案，它实际上是对Alex提供的答案的扩展(因此，所有功劳归功于他)，但是为了方便起见，它引入了属性列名称2-属性名称映射的映射.

I've decided to propose another answer, which actually extension to the answer provided by Alex (so all credits to him), but it introduces attributes for the sake of column-name-2-property-name mapping.

首先需要具有列名称的自定义属性:

First of all custom attribute to hold column name is needed:

[AttributeUsage(AttributeTargets.Property, Inherited = true)]
[Serializable]
public class MappingAttribute : Attribute
{
    public string ColumnName = null;
}

该属性必须应用于将从数据库行填充的类的那些属性:

The attribute must be applied to those properties of the class, that are to be populated from database row:

public class Product
{
    [Mapping(ColumnName = "product_id")]
    public int ProductId { get; private set; }

    [Mapping(ColumnName = "supplier_id")]
    public int SupplierId { get; private set; }

    [Mapping(ColumnName = "name")]
    public string Name { get; private set; }
    [Mapping(ColumnName = "price")]
    public decimal Price { get; private set; }
    [Mapping(ColumnName = "total_stock")]
    public int Stock { get; private set; }
    [Mapping(ColumnName = "pending_stock")]
    public int PendingStock { get; private set; }
}

除Alex所提议的以外，其余部分都使用该属性，只是该属性用于检索列名:

And rest goes as Alex proposed, except that the attribute is used to retrieve column name:

T MapToClass<T>(SqlDataReader reader) where T : class
{
        T returnedObject = Activator.CreateInstance<T>();
        PropertyInfo[] modelProperties = returnedObject.GetType().GetProperties();
        for (int i = 0; i < modelProperties.Length; i++)
        {
            MappingAttribute[] attributes = modelProperties[i].GetCustomAttributes<MappingAttribute>(true).ToArray();

            if (attributes.Length > 0 && attributes[0].ColumnName != null)
                modelProperties[i].SetValue(returnedObject, Convert.ChangeType(reader[attributes[0].ColumnName], modelProperties[i].PropertyType), null);
        }
        return returnedObject;
}

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