How can I get the value of a string property via R

Question

public class Foo
{
   public string Bar {get; set;}
}

How do I get the value of Bar, a string property, via reflection? The following code will throw an exception if the PropertyInfo type is a System.String

Foo f = new Foo();
f.Bar = "Jon Skeet is god.";

foreach(var property in f.GetType().GetProperties())
{
 object o = property.GetValue(f,null); //throws exception TargetParameterCountException for String type
}

It seems that my problem is that the property is an indexer type, with a System.String.

Also, how do I tell if the property is an indexer?

Answer 1

I couldn't reproduce the issue. Are you sure you're not trying to do this on some object with indexer properties? In that case the error you're experiencing would be thrown while processing the Item property. Also, you could do this:

public static T GetPropertyValue<T>(object o, string propertyName)
{
      return (T)o.GetType().GetProperty(propertyName).GetValue(o, null);
}

...somewhere else in your code...
GetPropertyValue<string>(f, "Bar");

Answer 2

You can just get the property by name:

Foo f = new Foo();
f.Bar = "Jon Skeet is god.";

var barProperty = f.GetType().GetProperty("Bar");
string s = barProperty.GetValue(f,null) as string;

Regarding the follow up question: Indexers will always be named Item and have arguments on the getter. So

Foo f = new Foo();
f.Bar = "Jon Skeet is god.";

var barProperty = f.GetType().GetProperty("Item");
if (barProperty.GetGetMethod().GetParameters().Length>0)
{
    object value = barProperty.GetValue(f,new []{1/* indexer value(s)*/});
}

Answer 3

Foo f = new Foo();
f.Bar = "x";

string value = (string)f.GetType().GetProperty("Bar").GetValue(f, null);

Answer 4

PropertyInfo propInfo = f.GetType().GetProperty("Bar");
object[] obRetVal = new Object[0];
string bar = propInfo.GetValue(f,obRetVal) as string;

Answer 5

var val = f.GetType().GetProperty("Bar").GetValue(f, null);

Answer 6

Foo f = new Foo();
f.Bar = "Jon Skeet is god.";

foreach(var property in f.GetType().GetProperties())
{
    if(property.Name != "Bar")
    {
         continue;
    }
    object o = property.GetValue(f,null); //throws exception TargetParameterCountException for String type
}

And here is for the followup:

class Test
{
    public class Foo
    {
        Dictionary<string, int> data =new Dictionary<string,int>();
        public int this[string index]
        {
            get { return data[index]; }
            set { data[index] = value; }
        }

        public Foo()
        {
            data["a"] = 1;
            data["b"] = 2;
        }
    }

    public Test()
    {
        var foo = new Foo();
        var property = foo.GetType().GetProperty("Item");
        var value = (int)property.GetValue(foo, new object[] { "a" });
        int i = 0;
    }
}