Create Generic Expression from string property name

Question

I have a variable called sortColumn, which contains the text of a column that I want to sort a query result by. I also have a generic repository which takes as a parameter

Answer 1

You kinda need to use the correct generic overload - which used to mean you had to use MakeGenericMethod; however, you can also use dynamic to avoid the need to use MakeGenericMethod here, for example (in this case via Where, but the important point is how it works):

IQueryable<Foo> source = new[] { new Foo { Bar = 123 } }.AsQueryable();
Expression<Func<Foo,bool>> typed =  x=>x.Bar == 123;

LambdaExpression untyped = typed;
IQueryable<Foo> filtered = Queryable.Where(source, (dynamic)untyped);

Note: you can't use extension methods here - hence why you need to use Queryable.*.

For an OrderBy example using your code:

var parameter = Expression.Parameter(typeof(Foo));
var memberExpression = Expression.Property(parameter, "Bar");
var lambdaExpression = Expression.Lambda(memberExpression, parameter);
LambdaExpression untyped = lambdaExpression;

IQueryable<Foo> sorted = Queryable.OrderBy(source, (dynamic)untyped);

var all = sorted.ToArray();

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Re the edit:

var parameter = Expression.Parameter(typeof(IRelationship));
var memberExpression = Expression.Property(
    Expression.Convert(parameter, typeof(IContract)), data.SortColumn);
var orderBy = Expression.Lambda(memberExpression, parameter);