Set operations: support when placed after client evaluation in projection

Test case:

public virtual Task Client_eval_Union_FirstOrDefault(bool isAsync)
    => AssertFirstOrDefault<Customer>(
        isAsync, cs => cs
            .Select(c => ClientSideMethod(c))
            .Union(cs));

Can probably be punted post-3.0 (can be easily worked around).

Issue Analytics

State:
Created 4 years ago
Reactions:7
Comments:30 (12 by maintainers)

Top GitHub Comments

34reactions

Maleaumecommented, May 1, 2020

Your example is not complete because you request on same table I have the use case with two tables with one different column but i want to make a union in a common object. I Can’t I have the same error

[TableA]
class A {
    public string NameA;
    public string DescriptionA;
}

[TableB]
class B {
    public string NameB;
    public string DescriptionB;
}

class UnionClass
{
    public string Name;
    public string Description;
}

I would like to

var queryableA  = Context.A.select( x => new UnionClass{ Name =x.NameA,Description = x.DescriptionA);
var queryableB = Context.Bselect( x => new UnionClass{ Name =x.NameB,Description = x.DescriptionB);

var queryUnion = queryableA.Union(queryableB)
var result = queryUnion .Select( x=> x.Name.contains("RE));

9reactions

rojicommented, May 1, 2020

@Maleaume @brandonsmith86 @BeejeeDS the only issue here is with set operations after a client projection - as long as you write your query to place the union before that, there’s no issue. You can typically do this by projecting to an anonymous type (which works fine and doesn’t require client translation) and doing everything you need on that. If you need to project out to your own type, do that at the end.

For example:

var result = ctx.A
    .Select(a => new { Name = a.NameA, Description = a.DescriptionA })
    .Union(ctx.B
        .Select(b => new { Name = b.NameB, Description = b.DescriptionB }))
    .Where(x => x.Name.StartsWith("a"))
    // Add any further operations to be executed in the database here
    .Select(x => new UnionClass
    {
        Name = x.Name,
        Description = x.Description
    })
    .ToList();