c# - MethodCallExpression is not setting up the orderby correctly -

i'm new expression business. modeling after example: https://msdn.microsoft.com/en-us/library/vstudio/bb882637(v=vs.110).aspx

i trying list of offices satisfies specific name. code works point need setup order by. keep getting error:

parameterexpression of type 'db.office' cannot used delegate parameter of type 'system.string' 

here code

        iqueryable<office> offices = getalloffices();         parameterexpression pe = expression.parameter(typeof(office), "office");         expression left = expression.property(pe, typeof(office).getproperty("officename"));         expression right = expression.constant(filterrequest.filters.value);         expression e1 = expression.equal(left, right);          expression predicatebody = e1;          methodcallexpression wherecallexpression = expression.call(             typeof(queryable),             "where",             new type[] { offices.elementtype },             offices.expression,             expression.lambda<func<office, bool>>(predicatebody, new parameterexpression[] { pe }));          methodcallexpression orderbycallexpression = expression.call(             typeof(queryable),             "orderby",             new type[] { offices.elementtype, offices.elementtype },             wherecallexpression,             expression.lambda<func<string, string>>(pe, new parameterexpression[] { pe }));          iqueryable<string> results = offices.provider.createquery<string>(orderbycallexpression); 

your query returns office, should

iqueryable<office> results = offices.provider.createquery<office>(orderbycallexpression); 

note orderby wrong...

it should like:

methodcallexpression orderbycallexpression = expression.call(     typeof(queryable),     "orderby",     new type[] { offices.elementtype, typeof(string) },     wherecallexpression,     expression.lambda<func<office, string>>(left, new parameterexpression[] { pe })); 

if want order officename. wrote was: .orderby(x => x) quite useless, because rows of table don't have ordering. have rewritten .orderby(x => x.officename)

perhaps want add .select(x => x.officename) after orderby

methodcallexpression selectcallexpression = expression.call(     typeof(queryable),     "select",     new type[] { offices.elementtype, typeof(string) },     orderbycallexpression,     expression.lambda<func<office, string>>(left, new parameterexpression[] { pe })); 

then is:

iqueryable<string> results = offices.provider.createquery<string>(selectcallexpression);