无法将类型为“ System.Int32”的对象转换为类型为“ System.Reflection.RuntimePropertyInfo”

Question

I have several entities that I'd like to transform. Here is an example:

 public class FromClass
{
    public string Id { get; set; }
    public string Name { get; set; }
    public string Type { get; set; }
    public string TimeStamp { get; set; }
}

public class ToClass
{
    public int Id { get; set; }
    public string Name { get; set; }
    public int TypeId { get; set; }
    public DateTime TimeStamp { get; set; }
}

I've made a class of how the transformation should be done for each property like this:

  public interface ITransformationRule
    {
        T Transform<T>(string value);
    }
    public class ColumnDescription
    {
        public string SourceColumnName { get; set; }
        public string TargetObjectProperty { get; set; }
        public ITransformationRule TransformationRule { get; set; }
    }

The source properties are always strings and the data is validated in a previous step so I know I can cast without exceptions. So for each property I have a transformationrules. Some transformations are plain casts while other do lookup in tables.

In the above example I'd have a List of ColumnDescriptions like this:

 public List<ColumnDescription> TransformationDescription = new List<ColumnDescription>
    {
        new ColumnDescription{SourceColumnName = "Id", TargetObjectProperty = "Id", TransformationRule = new IntegerTransformation() }

    };

etc... Now here is where I'm lost (or perhaps the ITransformationRule interface should look a little bit different). I've written the IntegerTransformationClass like this:

  public class IntegerTransformation : ITransformationRule
    {
        public T Transform<T>(string value)
        {
            object returnvalue = int.Parse(value);
            return (T) returnvalue;
        }
    }

finally I'm looping through the properties in the list like this:

foreach (var row in TransformationDescription)
        {
            ¨...
            var classType = row.TransformationRule.GetType();
            var methodInfo = classType.GetMethod("Transform");
            var generic = methodInfo.MakeGenericMethod(toProp.GetType());
            var parameters = new object[] { toProp.ToString() };
            var toValue = generic.Invoke(specialTransform.TransformationRule, parameters);
            toProp.SetValue(toObj, Convert.ChangeType(toValue, toProp.PropertyType), null);
        }

At runtime a get the exeption.Unable to cast object of type 'System.Int32' to type 'System.Reflection.RuntimePropertyInfo' when returning from the TransformationClass.

Perhaps I'm going about the problem in a totaly wrong way. Any input would be appreciated.

Answer 1

This line is the problem:

var generic = methodInfo.MakeGenericMethod(toProp.GetType());

You're calling GetType() on toProp - that will return some type derived from PropertyInfo . You actually want the property type, so just change it to:

var generic = methodInfo.MakeGenericMethod(toProp.PropertyType);