Question

Struggling with the following problem. I have an attribute that defines the name of the key in the database table. Using reflection, I initialize the value of a property or a field with that attribute. Everything is great until I define my property as an array:

[ConfigurationKey("TestArray")]
public int[] Array { get; set; }

Assuming that values stored in the table are comma-delimited strings, I am using the following to create an array:

return valueString.Split(',').Select(s => Convert.ChangeType(s, memberType.GetElementType())).ToArray();

This does create an array of elements but only array of Objects. As a result when I use FieldInfo or PropertyInfo to set a value, it throws with the exception “Cannot assign Object[] to Int32[]“.

Any ideas?

Answer 1

Well given that Convert.ChangeType is declared to return Object, I don’t think this is particularly surprising. ToArray() will create an array with the same element type as the input sequence, and Select is going to return an IEnumerable<object> in this case.

One option is to call Cast (and then ToArray) using reflection. To be honest, it’s probably going to be easiest to put everything into a single generic method, and call that by reflection:

public static T[] ParseToArray<T>(string valueString)
{
    return valueString.Split(',')
                      .Select(s => (T) Convert.ChangeType(s, typeof(T))
                      .ToArray();
}

Then you’d need:

Type t = memberType.GetElementType();
// Use the type declaring ParseToArray here
MethodInfo methodDefinition = typeof(...).GetMethod("ParseToArray");
MethodInfo method = methodDefinition.MakeGenericMethod(t);
object array = method.Invoke(null, new object[] { valueString });