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

I referred to the old System.Linq.Dynamic codebase in CodePlex and created a quite simple version from the perspective of implementation and invocation. Of course, it's an extension method on IQueryable

/*
using System;
using System.Linq;
using System.Linq.Expressions;
*/

public static IQueryable OrderBy(this IQueryable query, string orderByExpression)
{
    if (string.IsNullOrEmpty(orderByExpression))
        return query;

    string propertyName, orderByMethod;
    string[] strs = orderByExpression.Split(' ');
    propertyName = strs[0];

    if (strs.Length == 1)
        orderByMethod = "OrderBy";
    else
        orderByMethod = strs[1].Equals("DESC", StringComparison.OrdinalIgnoreCase) ? "OrderByDescending" : "OrderBy";

    ParameterExpression pe = Expression.Parameter(query.ElementType);
    MemberExpression me = Expression.Property(pe, propertyName);

    MethodCallExpression orderByCall = Expression.Call(typeof(Queryable), orderByMethod, new Type[] { query.ElementType, me.Type }, query.Expression
        , Expression.Quote(Expression.Lambda(me, pe)));

    return query.Provider.CreateQuery(orderByCall) as IQueryable;
}

Here is samples how to use it, tested for Entity Framework Core 3:

IQueryable query = dbContext.People;
query = query.OrderBy("FirstName"); // ORDER BY FirstName

IQueryable query = dbContext.People;
query = query.OrderBy("FirstName ASC"); // ORDER BY FirstName

IQueryable query = dbContext.People;
query = query.OrderBy("FirstName DESC"); // ORDER BY FirstName DESC