Boris Boris - 24 days ago 9
C# Question

Setting value in an array via reflection

Is there a way to set a single value in an array property via reflection in c#?

My property is defined like this:

double[] Thresholds { get; set; }


For "normal" properties I use this code to set it via reflection:

PropertyInfo pi = myObject.GetType().GetProperty(nameOfPropertyToSet);
pi.SetValue(myObject, Convert.ChangeType(valueToSet, pi.PropertyType), null);


How would I have to change this code to set the value in an array property at an arbitrary position?
Thanks!

BTW: I tried to use the index parameter, but that seems only to work for indexed properties, not properties that are arrays...

Answer

When you do:

obj.Thresholds[i] = value;

that is semantically equivalent to:

double[] tmp = obj.Thresholds;
tmp[i] = value;

which means you don't want a SetValue at all; rather, you want to use GetValue to obtain the array, and then mutate the array. If the type is known to be double[], then:

double[] arr = (double[]) pi.GetValue(myObject, null);
arr[i] = value;

otherwise perhaps the non-generic IList approach (since arrays implement IList):

IList arr = (IList) pi.GetValue(myObject, null);
arr[i] = value;

If it is a multi-dimensional array, you'll have to use Array in place of IList.