Elastic search nest dynamic query with object initializer NEST 5.x

But it doesnt work cause Field class doesnt accept type arguments.

You need to ensure that you include a using static directive for Nest.Infer i.e.

using static Nest.Infer;

with the rest of the using directives.

.Query(q => q.Bool(qb => qb.Must(m => m.MatchAll() && andQuery))));

No need to wrap in a Must(), just do

.Query(q => q.MatchAll() && andQuery)

which will wrap both queries in a bool query must clause. You also don't need to null check andQuery because NEST is smart enough to not combine the two queries if either or both are null.

if (!string.IsNullOrEmpty(queries.queryfields)){    var val = queries.queryfields;    TermQuery tq = new TermQuery    {        Field = queries.queryfields,        Value = val    };    if (andQuery == null)        andQuery = tq;    else        andQuery &= tq;    //QueryContainers.Add(tq);}

NEST has the concept of conditionless queries so you don't need to check it queries.queryfields is null or empty, simply build the query and add it to andQuery. So it would become

var val = queries.queryfields;andQuery &= new TermQuery{    Field = queries.queryfields,    Value = val};

Aside

All of the NEST documentation is generated from source code; you can trace back to the original source file by clicking on any edit link within the documentation. This will take you to a github page, such as this one for bool queries. From here, the document contains an important note that links back to the original source.