.NET Core使用配置绑定到带有阵列的选项 [英] .NET Core use Configuration to bind to Options with Array

问题描述

使用.NET Core Microsoft.Extensions.Configuration 是否可以将Configuration绑定到包含数组的对象?

ConfigurationBinder 具有方法

解决方案

该错误在您的输入定义中.该示例将键"Array"设置为字符串值"[1,2,3]"(在基于C#的InMemoryCollection中)，并假设它是解析的JSON样式.那是错的.只是没有解析.

配置系统中数组值的编码约定是通过在键后加上一个冒号和一个索引来重复该键.以下示例按您打算的方式工作:

  var config = new ConfigurationBuilder().AddInMemoryCollection(new List< KeyValuePair< string，string>>{新的KeyValuePair< string，string>("Array:0"，"1")，新的KeyValuePair< string，string>("Array:1"，"2")，新的KeyValuePair< string，string>("Array:2"，"3")}).建造(); 

如果使用JSON文件(此处是对AddJsonFile的附加调用)，也会发生冒号重复方案...

  {"mySecondArray":[1、2、3]} 

最终的组合配置将包含与上面的内存中用法相同的模式的键:

  Count = 8[0]:{[mySecondArray，]}[1]:{[mySecondArray:2，3]}[2]:{[mySecondArray:1、2]}[3]:{[mySecondArray:0，1]}[4]:{[Array，]}[5]:{[Array:2，3]}[6]:{[Array:1、2]}[7]:{[Array:0，1]} 

配置系统与诸如JSON/INI/XML/...之类的存储格式无关，本质上只是一个字符串->字符串字典，由冒号组成一个在键内的层次结构 .然后，

绑定可以通过约定解释某些层次结构，因此还可以绑定数组，集合，对象和字典.有趣的是，对于数组，它并不关心冒号后面的数字，而只是关心排序，将数字考虑在内，但也将字符串作为第二个选项(OrdinalIgnoreCase)进行排序.

Using the .NET Core Microsoft.Extensions.Configuration is it possible to bind to a Configuration to an object that contains an array?

ConfigurationBinder has a method BindArray, so I'd assume it would work.

But when I try it out I get an exception:

System.NotSupportedException: ArrayConverter cannot convert from System.String.

Here's my slimmed down code:

public class Test
{
   private class ExampleOption
   { 
      public int[] Array {get;set;}
   }

   [Test]
   public void CanBindArray()
   {
       // ARRANGE
       var config =
            new ConfigurationBuilder()
            .AddInMemoryCollection(new List<KeyValuePair<string, string>>
            {
                new KeyValuePair<string, string>("Array", "[1,2,3]")
            })
            .Build();

        var exampleOption= new ExampleOption();

        // ACT
        config.Bind(complexOptions); // throws exception

       // ASSERT
       exampleOption.ShouldContain(1);
   }
}

解决方案

The error is in your input definition. The sample sets a key "Array" to a string value of "[1,2,3]" (in the C# based InMemoryCollection) and makes the assumption it is parsed JSON style. That is wrong. It is just not parsed.

The encoding convention of array values in the config system is by repeating the key with a colon and an index behind it. The following sample works like you intend to do:

var config = new ConfigurationBuilder()
        .AddInMemoryCollection(new List<KeyValuePair<string, string>>
        {
            new KeyValuePair<string, string>("Array:0", "1"),
            new KeyValuePair<string, string>("Array:1", "2"),
            new KeyValuePair<string, string>("Array:2", "3")
        })
        .Build();

The colon-key-repeating scheme happens also if JSON file is used (here by an additional call to AddJsonFile) ...

{
  "mySecondArray":  [1, 2, 3]
}

the resulting combined configuration will contain the keys which follow the same pattern as illustrated for in-memory usage above:

Count = 8
[0]: {[mySecondArray, ]}
[1]: {[mySecondArray:2, 3]}
[2]: {[mySecondArray:1, 2]}
[3]: {[mySecondArray:0, 1]}
[4]: {[Array, ]}
[5]: {[Array:2, 3]}
[6]: {[Array:1, 2]}
[7]: {[Array:0, 1]}

The config system is agnostic to storage formats like JSON/INI/XML/... and is essentially just a string->string dictionary with colon making up a hierarchy within the key.

Bind is then able to interpret some of the hierarchy by conventions and therefore binds also arrays, collections, objects and dictionaries. Interestingly for arrays, it does not care about the numbers behind the colon but just iterate the children of the configuration section (here "Array") and take the values of the children. The sorting of the children again, takes the numbers into consideration but also sorts strings as a second option (OrdinalIgnoreCase).

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