GroupBy Clause: To be able to pass in a Column name as a string - group-by

Question

In EF, Order By allows a column name to be used to eg OrderBy("Description")
I need to be able to do some thing similar with GroupBy
Other posts have solutions when the column type is known
var groupByExpressionGN2 = GetGroupByExpressionGuidNull<DebtWaiver>("PersonUID");
...
// in the query
.GroupBy(groupByExpression2)
// the Expression function
private static Expression<Func<TEntity,Guid?>> GetGroupByExpressionGuidNull<TEntity>(string property)
{
var item = Expression.Parameter(typeof(TEntity), "gb");
var itemProperty = Expression.PropertyOrField(item, property);
var lambda = Expression.Lambda<Func<TEntity, Guid?>>(itemProperty, item);
return lambda;
}
But my users may select 1 of any columns by which to group by
So how can I make the function above return an expression for group by
I have tried this:
public static Expression<Func<T, object>> GetMember<T>(string memberName)// where T : EntityObject
{
ParameterExpression pe = Expression.Parameter(typeof(T), "p");
System.Reflection.PropertyInfo pi = typeof(T).GetProperty(memberName);
return (Expression<Func<T, object>>)Expression.Lambda<Func<T, object>>(Expression.Convert(Expression.Property(pe, pi), typeof(object)), pe);
}
but it produces : p =>Convert(p.PersonUID)
instead of:p =>p.PersonUID
Regards
GregJF

Answer 1

After a bit more testing (and a good night's sleep) I got the second method to work (Thanks to JA Rreyes )
My issue was that I was using this:
var groupByExpressionGN2 = GetGroupByExpressionGuidNull<DebtWaiver>("PersonUID");
...
// in the query
.GroupBy(groupByExpression2)
I should have being doing this:
var groupByExpression2 = GetMember<DebtWaiver>("PersonUID");
...
// in the query
.GroupBy(groupByExpression2.Compile())
You can use the second method in my original post( GetMember ), but I use this method('cos I like it!): Thanks: Taher Rahgooy
public static Expression<Func<T, object>> GetPropertySelector<T>(string propertyName)
{
var arg = Expression.Parameter(typeof(T), "gb");
var property = Expression.Property(arg, propertyName);
var conv = Expression.Convert(property, typeof(object));
var exp = Expression.Lambda<Func<T, object>>(conv, new ParameterExpression[] { arg });
return exp;
}
Regards
GregJF