使用动态方法（或通过其他方法）从通用方法中调用第三方程序集的重载方法？

Question

Update: Turns out there were details I had completely missed until I looked at the source code of the library I was using. Apologies for the bad example code starting out, was trying to focus on what I thought was relevant.

Working with FlatFiles NuGet library which has 25 overloads for a Property(...) method. I'm trying to dispatch the correct Property(...) overload from my generic method by using dynamic on a parameter I'm passing, but this isn't working. Here's what I tried:

using FlatFiles;
using FlatFiles.TypeMapping;

public class FixedWidthDataSource<FixedWidthRecordT> {
    public IFixedLengthTypeMapper<FixedWidthRecordT> Mapper
        = FixedLengthTypeMapper.Define<FixedWidthRecordT>()
    ;
    ...
    public void MapProperty<T>(
        Expression<Func<FixedWidthRecordT, T>> col
        , int width
        , string inputFormat = null
    ) {
        var window = new Window(width);
        Mapper.Property((dynamic)col, window);
    }
}

public class FixedWidthRecord
{
    public string First { get; set; }
    public string Last { get; set; }
}

//later
var fwds = new FixedWidthDataSource<FixedWidthRecord>();
fwds.MapProperty(c=>c.First, 5);

A few of the Property overloads:

Property(Expression<Func<FixedWidthRecordT, bool>> property, Window window);
Property(Expression<Func<FixedWidthRecordT, int>> property, Window window);
Property(Expression<Func<FixedWidthRecordT, string>> property, Window window);

The error I get is 'FlatFiles.TypeMapping.IFixedLengthTypeMapper<FixedWidthRecord>' does not contain a definition for 'Property' .

Looking at the source I see the there's an internal sealed class FixedLengthTypeMapper<TEntity> and this is the type of object that's being returned from the call to FixedLengthTypeMapper.Define<FixedWidthRecordT>() and assigned to Mapper . However, IFixedLengthTypeMapper does not have any definitions for Property(...) , only FixedLengthTypeMapper has them.

Hoping that's all relevant.

Answer 1

Maybe your case has something to do with this? RuntimeBinderException – “does not contain a definition for” .

That article gets that exception in the case of an anonymous object, but your case seems similar. Your assembly is trying to access something through dynamic it cannot normally see: an internal class in your case, an anonymous type in theirs.

Adding the [assembly: InternalsVisibleTo("Your.Assembly")] attribute on the library doesn't sound like a good option, but if you can build from source it could help temporarily. Or maybe with that info you could create a solid repro.

Answer 2

Here is what I finally did to get it working, although it's by using an interface not described in the library's usage documentation. I'm still curious how this could have otherwise been solved (say for instance, if the IFixedLengthTypeConfiguration interface I'm using in the solution were also defined as internal).

using FlatFiles;
using FlatFiles.TypeMapping;

public class FixedWidthDataSource<FixedWidthRecordT> {
    public IFixedLengthTypeConfiguration<FixedWidthRecordT> Configuration
        = FixedLengthTypeMapper.Define<FixedWidthRecordT>()
    ;
    public IFixedLengthTypeMapper<FixedWidthRecordT> Mapper;
    public FixedWidthDataSource() {
        Mapper = (IFixedLengthTypeMapper<FixedWidthRecordT>)Configuration;
    }
    ...
    public void MapProperty<T>(
        Expression<Func<FixedWidthRecordT, T>> col
        , int width
        , string inputFormat = null
    ) {
        var window = new Window(width);
        Configuration.Property((dynamic)col, window);
    }
}

public class FixedWidthRecord
{
    public string First { get; set; }
    public string Last { get; set; }
}

//later
var fwds = new FixedWidthDataSource<FixedWidthRecord>();
fwds.MapProperty(c=>c.First, 5);