Elasticsearch .net Client Nest querycontainer always null

Question

Trying to filter results dynamically in a function by building a querycontainer which is always null. I don't undestand why because when I debug, I see that q variable is filled within the function but when I check the value of it, it is always null. Example code is below. Do you have any idea what I do wrong?

Thank you.

QueryContainer q = null;

        if (!ProductType.HasValue || (ProductType.HasValue && ProductType.Value == B2CVariables.PRODUCTTYPE_PRODUCT))
        {
            q = Query<ProductModel>.Term(t => t.Field(u => u.ProductTypeID == B2CVariables.PRODUCTTYPE_PRODUCT));
            q &= Query<ProductModel>.Term(t => t.Field(u => u.Stocks.Any() ? u.Stocks.Any(z => z.StatusID == B2CVariables.STATUS_PRODUCT_ONLINE && (!z.CheckStockStatus || (z.CheckStockStatus && z.CurrentStockCount > 0))) : false));
        }

Answer 1

The construction of the query is not correct according to the signature of a Term query constructed with the static Query<T> type.

Field(Func<T, object>) is a strongly typed expression to get the field that the query should operate on and the value with which the field must match for a term query should be specified using .Value(object value). Here's an examplem assuming the following setup

public static class B2CVariables
{
    public const int PRODUCTTYPE_PRODUCT = 2;

    public const int STATUS_PRODUCT_ONLINE = 1;
}

public class ProductModel
{
    public IList<Stock> Stocks { get; set;}

    public int ProductTypeID { get; set;}
}

public class Stock
{
    public int StatusID { get; set;}

    public bool CheckStockStatus { get; set;}

    public int CurrentStockCount { get; set;}
}

The query

if (!ProductType.HasValue || (ProductType.HasValue && ProductType.Value == B2CVariables.PRODUCTTYPE_PRODUCT))
{
    q = Query<ProductModel>.Term(t => t
            .Field(u => u.ProductTypeID)
            .Value(B2CVariables.PRODUCTTYPE_PRODUCT));

    q &= Query<ProductModel>.Term(t => t
             .Field(u => u.Stocks.First().StatusID)
             .Value(B2CVariables.STATUS_PRODUCT_ONLINE)) && 
         (Query<ProductModel>.Term(t => t
              .Field(u => u.Stocks.First().CheckStockStatus)
              .Value(false)) ||          
         (Query<ProductModel>.Term(t => t
             .Field(u => u.Stocks.First().CheckStockStatus)
             .Value(true)) && 
          Query<ProductModel>.Range(t => t
              .Field(u => u.Stocks.First().CurrentStockCount)
              .GreaterThan(0))));
}

u.Stocks.First().StatusID is an expression to get a status id of a child object on ProductModel; the fact that we used .First() doesn't mean that we are asking for the first status id, it's just an expression that determines how to access status id in a concise manner. See the section on field inference for more details.

Because Query<T>.Term(t => t.Field(u => u.Field).Value(value)) can get long winded when combining many queries, there is a shorthand Query<T>.Term(t => t.Field, value) that can be used instead (it's shorter in practice, even if it looks almost the same in this example due to indentation!)

if (!ProductType.HasValue || (ProductType.HasValue && ProductType.Value == B2CVariables.PRODUCTTYPE_PRODUCT))
{
    q = Query<ProductModel>.Term(
            t => t.ProductTypeID, 
            B2CVariables.PRODUCTTYPE_PRODUCT);

    q &= Query<ProductModel>.Term(
             t => t.Stocks.First().StatusID, 
             B2CVariables.STATUS_PRODUCT_ONLINE) && 
         (Query<ProductModel>.Term(
             t => t.Stocks.First().CheckStockStatus, 
             false) ||       
         (Query<ProductModel>.Term(
             t => t.Stocks.First().CheckStockStatus, 
             true) && 
          Query<ProductModel>.Range(t => t
              .Field(u => u.Stocks.First().CurrentStockCount)
              .GreaterThan(0))));
}

Both produce the following query

{
  "bool": {
    "must": [
      {
        "term": {
          "productTypeID": {
            "value": 2
          }
        }
      },
      {
        "term": {
          "stocks.statusID": {
            "value": 1
          }
        }
      },
      {
        "bool": {
          "should": [
            {
              "term": {
                "stocks.checkStockStatus": {
                  "value": false
                }
              }
            },
            {
              "bool": {
                "must": [
                  {
                    "term": {
                      "stocks.checkStockStatus": {
                        "value": true
                      }
                    }
                  },
                  {
                    "range": {
                      "stocks.currentStockCount": {
                        "gt": 0.0
                      }
                    }
                  }
                ]
              }
            }
          ]
        }
      }
    ]
  }
}

However, this query is probably not going to do what you want; Because there is a bool query that combines two queries across a child object (a term query on checkStockStatus and a range on currentStockcount), the Stock object should be modelled as a nested object such that a match for both queries must be from the same stock object.

Once modeled as a nested object, the query would become

int? ProductType = 2;
QueryContainer q = null;

if (!ProductType.HasValue || (ProductType.HasValue && ProductType.Value == B2CVariables.PRODUCTTYPE_PRODUCT))
{
    q = Query<ProductModel>.Term(t => t
        .Field(u => u.ProductTypeID)
        .Value(B2CVariables.PRODUCTTYPE_PRODUCT));

    q &= Query<ProductModel>.Nested(n => n
            .Path(u => u.Stocks.First())
            .Query(nq => nq
                .Term(t => t
                    .Field(u => u.Stocks.First().StatusID)
                    .Value(B2CVariables.STATUS_PRODUCT_ONLINE)) &&

                (nq.Term(t => t
                    .Field(u => u.Stocks.First().CheckStockStatus)
                    .Value(false)) ||
                (nq.Term(t => t
                    .Field(u => u.Stocks.First().CheckStockStatus)
                    .Value(true)
                ) && nq.Range(t => t
                    .Field(u => u.Stocks.First().CurrentStockCount)
                    .GreaterThan(0)
                )))
            )
        );
}

with the query json

{
  "bool": {
    "must": [
      {
        "term": {
          "productTypeID": {
            "value": 2
          }
        }
      },
      {
        "nested": {
          "query": {
            "bool": {
              "must": [
                {
                  "term": {
                    "stocks.statusID": {
                      "value": 1
                    }
                  }
                },
                {
                  "bool": {
                    "should": [
                      {
                        "term": {
                          "stocks.checkStockStatus": {
                            "value": false
                          }
                        }
                      },
                      {
                        "bool": {
                          "must": [
                            {
                              "term": {
                                "stocks.checkStockStatus": {
                                  "value": true
                                }
                              }
                            },
                            {
                              "range": {
                                "stocks.currentStockCount": {
                                  "gt": 0.0
                                }
                              }
                            }
                          ]
                        }
                      }
                    ]
                  }
                }
              ]
            }
          },
          "path": "stocks"
        }
      }
    ]
  }
}