Multiple Dynamic Column Select Expression Tree

Question

Need: To allow the user to select 3 columns to return from a local database. With the help of another post I was able to return 1 column for a different application in the program, and I figured I could apply the same process here, but I'm not seeing how to allow the user to select multiple columns within the same query. I see where Func<> accepts up to 17 overloads where all but one can be fields, but that doesn't seem to be the right approach.

Example:

TableX has the following columns: A,B,C,D,E,F

A B C D E F
1 2 6 2 4 6
3 6 2 7 2 1
4 8 0 3 7 6

User Selects columns A, D, F

Query should return:

1 2 6
3 7 1
4 3 6

SQL statement to achieve this would be the following:

col1 = user selection 1.SelectedItem.ToString();
col2 = user selection 2.SelectedItem.ToString();
col3 = user selection 3.SelectedItem.ToString();


SELECT @col1, @ col2, @col3 FROM TableX;

Linq statement would be something like the following if I knew the fields that were going to be selected before runtime:

(from UserPageTbl in conn.Table<TableX>()
                         select new
                         {
                             TableX.A,
                             TableX.B,
                             TableX.C,
                         }

                       ).ToList();

*but I don't see how to parameterize selections in LINQ and pass them as a field in a select statement.

I get the concept of stacking sections of the Linq Expressions using an Expression Tree to return 1 column (like an ORDERBY and a WHERE clause), but I don't see how to do that for multiple columns. It would work the same way to build a SQL statement. I tried to use the Expression.New thinking that I needed the new {} to generate a list of the return columns and that didn't seem to be the right process.

Current Set Up: Using an extension method with an expression tree and lambda expression with LINQ to return 1 column. This does work. See Code below:

private static IQueryable<TResult> SelectByFieldName<T, TResult>(IQueryable<T> query, string fieldName)
{
    var param = Expression.Parameter(typeof(T), "e");
    Expression body = Expression.PropertyOrField(param, fieldName);
    if (body.Type != typeof(TResult))
        body = Expression.Convert(body, typeof(TResult));
    var lambda = Expression.Lambda<Func<T, TResult>>(body, param);
    return query.Select(lambda);

}

Problem: I cannot figure out how to add additional columns to the lambda expression to return multiple selected columns.

Trying to combine the items in a Select Query lambda expression as above:

    private static IQueryable<TResult> GraphFields<T, a, b, c, TResult>(IQueryable<T> query, string aField, string bField, string cField)
    {
        var param = Expression.Parameter(typeof(T), "e");
        Expression aFieldBody = Expression.PropertyOrField(param, aField);
        if (aFieldBody.Type != typeof(TResult))
            aFieldBody = Expression.Convert(aFieldBody, typeof(TResult));
        Expression bFieldBody = Expression.PropertyOrField(param, bField);
        if (bFieldBody.Type != typeof(TResult))
            bFieldBody = Expression.Convert(bFieldBody, typeof(TResult));
        Expression cFieldBody = Expression.PropertyOrField(param, cField);
        if (cFieldBody.Type != typeof(TResult))
            cFieldBody = Expression.Convert(cFieldBody, typeof(TResult));
        
        var lambdaA = Expression.Lambda<Func<T, TResult>>(aFieldBody, param);
        var lambdaB = Expression.Lambda<Func<T, TResult>>(bFieldBody, param);
        var lambdaC = Expression.Lambda<Func<T, TResult>>(cFieldBody, param);

        return query.Select(lambdaA, lambdaB, lambdaC);


    }

I've also tried writing the following using the field variables in the "Select" statement,

return query.Select(new { aFieldBody, bFieldBody, cFieldBody }, param);

I've tried the following, because I thought multiple overloads would allow me to

var lambda = Expression.Lambda<Func<T,a,b, TResult>>(aFieldBody, bFieldBody, cFieldBody, param);

I've also researched adding it to the PropertyOrField but it only accepts two overloads one for the parameter expression and 1 for the field name. I just can't figure out how to append more columns.

Tried using Linq.Dynamic.Core, by doing the following:

var list = conn.Table<Table1>()
        .Where(t => t.User_ID == user).Distinct().ToList();

var listquery = list.AsQueryable();
        var Values = listquery
                .Select("new {Field1}")
                .ToDynamicList();

I get the following exception: System.TypeInitializationException thrown The type initializer for System.Linq.Dynamic.Core.Parser.EnumerationsFromMscorlib threw an exception.