Get property value from string using reflection in

Question

I am trying implement the Data transformation using Reflection¹ example in my code.

The GetSourceValue function has a switch comparing various types, but I want to remove these types and properties and have GetSourceValue get the value of the property using only a single string as the parameter. I want to pass a class and property in the string and resolve the value of the property.

Is this possible?

¹ _{Web Archive version of original blog post}

Answer 1

If I use the code from Ed S. I get

'ReflectionExtensions.GetProperty(Type, string)' is inaccessible due to its protection level

It seems that GetProperty() is not available in Xamarin.Forms. TargetFrameworkProfile is Profile7 in my Portable Class Library (.NET Framework 4.5, Windows 8, ASP.NET Core 1.0, Xamarin.Android, Xamarin.iOS, Xamarin.iOS Classic).

Now I found a working solution:

using System.Linq;
using System.Reflection;

public static object GetPropValue(object source, string propertyName)
{
    var property = source.GetType().GetRuntimeProperties().FirstOrDefault(p => string.Equals(p.Name, propertyName, StringComparison.OrdinalIgnoreCase));
    return property?.GetValue(source);
}

Source

Answer 2

The following code is a Recursive method for displaying the entire hierarchy of all of the Property Names and Values contained in an object's instance. This method uses a simplified version of AlexD's GetPropertyValue() answer above in this thread. Thanks to this discussion thread, I was able to figure out how to do this!

For example, I use this method to show an explosion or dump of all of the properties in a WebService response by calling the method as follows:

PropertyValues_byRecursion("Response", response, false);

public static object GetPropertyValue(object srcObj, string propertyName)
{
  if (srcObj == null) 
  {
    return null; 
  }
  PropertyInfo pi = srcObj.GetType().GetProperty(propertyName.Replace("[]", ""));
  if (pi == null)
  {
    return null;
  }
  return pi.GetValue(srcObj);
}

public static void PropertyValues_byRecursion(string parentPath, object parentObj, bool showNullValues)
{
  /// Processes all of the objects contained in the parent object.
  ///   If an object has a Property Value, then the value is written to the Console
  ///   Else if the object is a container, then this method is called recursively
  ///       using the current path and current object as parameters

  // Note:  If you do not want to see null values, set showNullValues = false

  foreach (PropertyInfo pi in parentObj.GetType().GetTypeInfo().GetProperties())
  {
    // Build the current object property's namespace path.  
    // Recursion extends this to be the property's full namespace path.
    string currentPath = parentPath + "." + pi.Name;

    // Get the selected property's value as an object
    object myPropertyValue = GetPropertyValue(parentObj, pi.Name);
    if (myPropertyValue == null)
    {
      // Instance of Property does not exist
      if (showNullValues)
      {
        Console.WriteLine(currentPath + " = null");
        // Note: If you are replacing these Console.Write... methods callback methods,
        //       consider passing DBNull.Value instead of null in any method object parameters.
      }
    }
    else if (myPropertyValue.GetType().IsArray)
    {
      // myPropertyValue is an object instance of an Array of business objects.
      // Initialize an array index variable so we can show NamespacePath[idx] in the results.
      int idx = 0;
      foreach (object business in (Array)myPropertyValue)
      {
        if (business == null)
        {
          // Instance of Property does not exist
          // Not sure if this is possible in this context.
          if (showNullValues)
          {
            Console.WriteLine(currentPath  + "[" + idx.ToString() + "]" + " = null");
          }
        }
        else if (business.GetType().IsArray)
        {
          // myPropertyValue[idx] is another Array!
          // Let recursion process it.
          PropertyValues_byRecursion(currentPath + "[" + idx.ToString() + "]", business, showNullValues);
        }
        else if (business.GetType().IsSealed)
        {
          // Display the Full Property Path and its Value
          Console.WriteLine(currentPath + "[" + idx.ToString() + "] = " + business.ToString());
        }
        else
        {
          // Unsealed Type Properties can contain child objects.
          // Recurse into my property value object to process its properties and child objects.
          PropertyValues_byRecursion(currentPath + "[" + idx.ToString() + "]", business, showNullValues);
        }
        idx++;
      }
    }
    else if (myPropertyValue.GetType().IsSealed)
    {
      // myPropertyValue is a simple value
      Console.WriteLine(currentPath + " = " + myPropertyValue.ToString());
    }
    else
    {
      // Unsealed Type Properties can contain child objects.
      // Recurse into my property value object to process its properties and child objects.
      PropertyValues_byRecursion(currentPath, myPropertyValue, showNullValues);
    }
  }
}

Answer 3

 public static object GetPropValue(object src, string propName)
 {
     return src.GetType().GetProperty(propName).GetValue(src, null);
 }

Of course, you will want to add validation and whatnot, but that is the gist of it.

Answer 4

The method to call has changed in .NET Standard (as of 1.6). Also we can use C# 6's null conditional operator.

using System.Reflection; 
public static object GetPropValue(object src, string propName)
{
    return src.GetType().GetRuntimeProperty(propName)?.GetValue(src);
}

Answer 5

Using PropertyInfo of the System.Reflection namespace. Reflection compiles just fine no matter what property we try to access. The error will come up during run-time.

    public static object GetObjProperty(object obj, string property)
    {
        Type t = obj.GetType();
        PropertyInfo p = t.GetProperty("Location");
        Point location = (Point)p.GetValue(obj, null);
        return location;
    }

It works fine to get the Location property of an object

Label1.Text = GetObjProperty(button1, "Location").ToString();

We'll get the Location : {X=71,Y=27} We can also return location.X or location.Y on the same way.

Answer 6

About the nested properties discussion, you can avoid all the reflection stuff if you use the DataBinder.Eval Method (Object, String) as below:

var value = DataBinder.Eval(DateTime.Now, "TimeOfDay.Hours");

Of course, you'll need to add a reference to the System.Web assembly, but this probably isn't a big deal.