传递空JS数组控制器发出空 [英] Passing empty js array to controller gives null
问题描述
下面是我的模型,它是一个WCF Proxy类
Here is my model which is a WCF Proxy class
public class MyModel
{
public Employees[] MyEmpls{get;set;}
public int Id{get;set;}
public OrgName{get;set;}
}
传递与 MyEmpls下面一个JSON结构对象作为空数组
MVC的控制器。
["Id":12, "MyEmpls":[], "OrgName":"Kekran Mcran"]
控制器
[HttpPost]
public ActionResult SaveOrg(MyModel model)
{
//model.MyEmpls is null here
}
我期待 mode.MyEmpls
为空的C#阵列,而不是空。可能有人帮助我在这里?我们需要编写一个自定义模型粘合剂呢?
I am expecting mode.MyEmpls
as empty c# array and not null. Could some one help me here? Do we need to write a custom model binder for this?
推荐答案
我认为一些其他的答案已经错过了这个问题的意思是:为什么默认的MVC模型绑定绑定一个空的JSON数组而不是空的空C#数组?
I think that some of the other answers have missed the meaning of the question: why does the default MVC model binder bind an empty Json array to null instead of an empty C# array?
好吧,我不能告诉你他们为什么这样做,但我可以告诉你它发生在哪里。对于MVC的源代码可以在这里codePLEX为:<一href=\"http://aspnetwebstack.$c$cplex.com/SourceControl/latest\">http://aspnetwebstack.$c$cplex.com/SourceControl/latest.你要找的文件是<一个href=\"http://aspnetwebstack.$c$cplex.com/SourceControl/latest#src/System.Web.Mvc/ValueProviderResult.cs\">ValueProviderResult.cs在这里你可以看到:
Well, I can't tell you why they did that, but I can show you where it happens. The source for MVC can be found on CodePlex here: http://aspnetwebstack.codeplex.com/SourceControl/latest. The file you're looking for is ValueProviderResult.cs where you can see:
private static object UnwrapPossibleArrayType(CultureInfo culture, object value, Type destinationType)
{
if (value == null || destinationType.IsInstanceOfType(value))
{
return value;
}
// array conversion results in four cases, as below
Array valueAsArray = value as Array;
if (destinationType.IsArray)
{
Type destinationElementType = destinationType.GetElementType();
if (valueAsArray != null)
{
// case 1: both destination + source type are arrays, so convert each element
IList converted = Array.CreateInstance(destinationElementType, valueAsArray.Length);
for (int i = 0; i < valueAsArray.Length; i++)
{
converted[i] = ConvertSimpleType(culture, valueAsArray.GetValue(i), destinationElementType);
}
return converted;
}
else
{
// case 2: destination type is array but source is single element, so wrap element in array + convert
object element = ConvertSimpleType(culture, value, destinationElementType);
IList converted = Array.CreateInstance(destinationElementType, 1);
converted[0] = element;
return converted;
}
}
else if (valueAsArray != null)
{
// case 3: destination type is single element but source is array, so extract first element + convert
if (valueAsArray.Length > 0)
{
value = valueAsArray.GetValue(0);
return ConvertSimpleType(culture, value, destinationType);
}
else
{
// case 3(a): source is empty array, so can't perform conversion
return null;
}
}
// case 4: both destination + source type are single elements, so convert
return ConvertSimpleType(culture, value, destinationType);
}
}
有趣的部分是案例3:
The interesting part is "case 3":
else
{
// case 3(a): source is empty array, so can't perform conversion
return null;
}
您可以通过初始化在它的构造模型阵列回避这个问题。在我的源快速阅读中,我不能告诉你为什么他们不能返回一个空数组或为什么他们决定不,但它应该为有趣的阅读。
You can sidestep this issue by initialising your array on the model in its constructor. In my quick reading of the source I can't tell you why they can't return an empty array or why they decide not to, but it should make for interesting reading.
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