Generate EF orderby expression by string

Question

I want to generate expression by string parameter,some code like:

private Expression> Generate(string orderby)
{
    switch (orderb         


        

Answer 1

public static IQueryable OrderByHelper(this IQueryable source, string propertyName, string sortDirection)
    {

        try
        {
            if (source == null)
            {
                return source;
            }
            if (propertyName == null)
            {
                return source;
            }

            propertyName = propertyName.First().ToString().ToUpper(new CultureInfo("en-US", false)) + propertyName.Substring(1);
            var type = typeof(T);
            var arg = Expression.Parameter(type, "x");

            var propertyInfo = type.GetProperty(propertyName);
            var mExpr = Expression.Property(arg, propertyInfo);
            type = propertyInfo.PropertyType;

            var delegateType = typeof(Func<,>).MakeGenericType(typeof(T), type);
            var lambda = Expression.Lambda(delegateType, mExpr, arg);

            var methodName = !string.IsNullOrEmpty(sortDirection) && sortDirection.ToLower(new CultureInfo("en-US", false)) == "desc" ? "OrderByDescending" : "OrderBy";
            var orderedSource = typeof(Queryable).GetMethods().Single(
                method => method.Name == methodName
                        && method.IsGenericMethodDefinition
                        && method.GetGenericArguments().Length == 2
                        && method.GetParameters().Length == 2)
                .MakeGenericMethod(typeof(T), type)
                .Invoke(null, new object[] { source, lambda });

            return (IQueryable)orderedSource;
        }
        catch (Exception)
        {

            return source;
        }
    }