如何转换表达式 <Func<TSource,string> &gt;表达 <Func<object,string> &gt;

Question

I am creating an expression dynamically which I pass into some method but that method accepts that expression in different way. It throws exception:

Object of type
'System.Linq.Expressions.Expression`1[System.Func`2[Common.Domain.ViewModels.Dealer.CustomerGridViewModel,System.String]]'
cannot be converted to type
'System.Linq.Expressions.Expression`1[System.Func`2[System.Object,System.String]]'

I have tried the answer from Using Expression to 'Cast' Func<object, object> to Func<T, TRet> but that is not working for me.

My expression is

Expression<Func<CustomerViewModel, string>> 

but I want result as

Expression<Func<object, string>>

Answer 1

Despite the fact that such cast is dangerous as the target method isn't guaranteed to operate only on CustomerViewModel , the following code makes adapter expression which accepts a parameter of Object type, tries to cast it to the CustomerViewModel and calls the original expression internally:

var objParam = Expression.Parameter(typeof(object));
var call = Expression.Invoke(inputExpression, Expression.Convert(objParam, typeof(Foo)));
var outputExpression = Expression.Lambda<Func<object, string>>(call, objParam);

where inputExpression is an original expression of type Expression<Func<CustomerViewModel, string>> and outputExpression is new expression of type Expression<Func<object, string>> which can be passed to your method.