NetTopologySuite.Geometries.MultiPoint需要具有0个参数的构造函数

Question

我试图用Automapper映射一个NetTopologySuite.Geometries.MultiPoint，但我一直收到错误消息System.ArgumentException: NetTopologySuite.Geometries.MultiPoint needs to have a constructor with 0 args or only optional args。

var config = new MapperConfiguration(cfg => {});
var mapper = config.CreateMapper();
     
MultiPoint mp1 = null;
MultiPoint mp2 = mapper.Map<MultiPoint>(mp1); // throws

实际上，这个类型没有带0个参数的构造函数。我尝试指定如何实例化该类型：

new MapperConfiguration(cfg => {
    cfg.CreateMap<MultiPoint, MultiPoint>()
        .ConstructUsing(mp => new MultiPoint((Point[])mp.Geometries));
});

同样的错误。为了用更简单的代码重现，我创建了一个没有0 args构造函数的类。

var config = new MapperConfiguration(cfg => { });
var mapper = config.CreateMapper();

TestCollection tc1 = null;
TestCollection tc2 = mapper.Map<TestCollection>(tc1); // throws

class Test
{
}

class TestCollection : IEnumerable<Test>
{
    public TestCollection(Test[] tests) => Tests = tests;
    public Test[] Tests { get; set; }
    public IEnumerator<Test> GetEnumerator() => new TestCollectionEnumerator();
    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
}

class TestCollectionEnumerator : IEnumerator<Test>
{
    object IEnumerator.Current => Current;
    public Test Current { get; }
    public bool MoveNext() => false;
    public void Reset() { }
    public void Dispose() { }
}

是bug，还是我漏掉了什么？

Answer 1

我想是因为你的MultiPoint是空的。使用Nettopologysuite的多点(内部指针不能为空)。

MultiPoint mp1 = null;

至

MultiPoint mp1 = NetTopologySuite.Geometries.MultiPoint.Empty;