Read elements of an array of objects using C# reflection

Question

How can I get the list of elements and datatypes of an array of an object in c# with reflections?

Scenario: I have a method with an array parameter in my web service (asmx). Using reflection I am reading the method parameters and loop through the properties. Here is my code:

Example: I have a webservice http://localhost/services/myservice.asmx. It has a method string GetServiceData(context mycontext). context class has following properties

- string name
- Account[] accounts

Account in turn has

- string acct_name
- string acct_address

I need to read the service dynamically to generate the following output

<GetServiceData>
    <mycontext>
        <name>string</name>
        <accounts>
            <acct_name>string</acct_name>
            <acct_address>string</acct_address>
        </accounts>
    </mycontext>
</GetServiceData>

To do so I am dynamically reading the MethodInfo and get all the parameters. Then I loop through the parameters to get the list of all the properties and the datatypes. If there is an array element in the properties then I need to get all the elements of that array element.

Solution (Thanks to Ani)

foreach (MethodInfo method in methods)
{
    sb.Append("<" + method.Name + ">");
    ParametetInfo parameters = method.GetParameters();
    foreach(ParameterInfo parameter in parameters)
    {
        sb.Append("<" + parameter.Name + ">");
        if (IsCustomType(parameter.ParameterType))
        {
           sb.Append(GetProperties(parameter.ParameterType));
        }
        else
        {
            sb.Append(parameter.ParameterType.Name);
        }
        sb.Append("</" + parameter.Name + ">");
    }
    sb.Append("</" + sMethodName + ">");
}

GetProperties() method reads the type and actually loop through each property and add it to string object. In this method I want to check if the property is an array then get all the elements and type for it.

public static string GetProperties(Type type)
{
    StringBuilder sb = new StringBuilder();
    foreach(PropertyInfo property in type.GetProperties())
    {
        sb.Append("<" + property.Name + ">");

        if (property.PropertyType.IsArray)
        {
            Type t = property.PropertyType.GetElementType();
            sb.Append(GetProperties(t));
        }
        else
        {
            sb.Append(property.PropertyType.name);
        }
    }
    sb.ToString();
}

Ani · Accepted Answer · 2011-03-14 20:19:29Z

9

I think you're for looking for theType.IsArray property (indicates whether a type is an array) and the Type.GetElementType method (gets, amongst other things, the element-type of an array). Do note that the element-type of the array isn't necessarily the same as the specific run-time type of each of the elements of the array; polymorphism could come into play.

Of course, to simply get the values, you can rely on array-covariance: cast the value of the property (I assume you're using PropertyInfo.GetValue somewhere) to an object[] and foreach that as usual.

EDIT:

Your update is quite confusing. If you already have an object that you think might be an array; you might as well do:

object obj = ...

object[] array = obj as object[];

if(array != null)
{
   foreach(object item in array)
   {
      ...
   }      
}

It really appears like you're confusing meta-data with real-data here. You can't actually enumerate any array if all you have is a System.Type that represents an array-type.

EDIT:

I think I've finally understood what you want to do. Just use Type.GetElementType to get the array's element-type, and then get that type's properties (recursively?). You're probably going to change your design a bit to able to get the XML output you want. XML represents a hierarchy; but your method's return-type is just a Dictionary<string, string>, which is a flat data-structure.

edited Mar 14, 2011 at 20:19

answered Mar 14, 2011 at 18:54

Ani

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8 Comments

Sri Reddy Over a year ago

Ani, I am able to check for IsArray but how can I now determine all the elements of that array type. Example: accounts is of type Account[] and it has 3 elements - acct_name (string), acct_address (string), acct_ph (string[]). how to loop through each element of accounts to add element/type in my dictionary?

Ani Over a year ago

@user465876: Your code sample doesn't provide any means to actually get the array: your GetProperties method accepts only a Type, which represents metadata only. As I mentioned, you probably want ProperyInfo.GetValue (with a reference to the actual object in question). Then cast the result of that call to object[]. Then you can enumerate the array with a foreach loop or similar, calling GetType() on each member in turn (after a null-check). Does that help?

Sri Reddy Over a year ago

@Ani, may be i am missing something here. In my code, the first snippet, I am just reading the method and the parameters. What will be the actual object there? If my method defination in WebService is something like GetServiceData(context mycontext). context type has - string name, Account[] accounts. What you mentioned will work if I am checking for the return type. I can change my GetProperties to accept a parameter of type object and then do what you mentioned. But not sure how can i do the same for parameters? I have added an example code above, please verify.

Ani Over a year ago

Parameters aren't the same as arguments; a MethodInfo also represents metadata only. You're going to have to actually get an object that has the real data from somewhere; I can't say where without more info.

Sri Reddy Over a year ago

Ani, thanks for your time here. More Info, I am trying to read the webservice (asmx) url and generate a proxy. Then I give user an ability to select a method. When user selects a method, I want to execute a code which will basically build a parameter list with datatypes. If the parameter has a custom type then I drill down further to provide that list too. I am able to read all the parameters and their hierarchy but for arrays I am getting difficulty. Now can you point me how to get an object that you mentioned?

|

SwDevMan81 · Accepted Answer · 2011-03-14 20:24:14Z

1

You can check the PropertyInfo.PropertyType Property. Like this:

if (propertyInfo.PropertyType.IsArray)
{
   // Type is an array
}

Update: If you just want to get the properties of the array, you can use GetElementType like this:

    ...
    //How to check for an array??? and add it to objProp dictionary
    if (property.PropertyType.IsArray)
    {
        //??? how to read all the elements of an array 
        objProp = GetProperties(property.PropertyType.GetElementType());
    }
    ...

edited Mar 14, 2011 at 20:24

answered Mar 14, 2011 at 18:57

SwDevMan81

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2 Comments

Sri Reddy Over a year ago

how can I now determine all the elements of that array type. Example: accounts is of type Account[] and it has 3 elements - acct_name (string), acct_address (string), acct_ph (string[]). how to loop through each element of accounts to add element/type in my dictionary?

SwDevMan81 Over a year ago

@user - You can use Type.GetElementType() to determine the array type and just call your function again with the new type. See my update

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