Apply multiple conditions and null value check in Linq query

Question

Need to check If body data Null and if Null filed, no need to check the particular WHERE clause. How can I add multiple WHERE and OR clauses with NULL checking? In CountryDialCodeFields, some fields can be null sometimes.

 public class CountryDialCodeFields
    {
        public string countryCode { get; set; }
        public string countryName { get; set; }
        public string dialCode { get; set; }
        public string currencyCode { get; set; }
    }


[HttpGet("/api/country-details")]
public IActionResult CountryDetailGet(CountryDialCodeFields BodyData)
{
var CountryDataSet22 = CountryCodeDbContext.Countrydetails.Where( x => (BodyData.countryCode != null ? x.Countrycode == BodyData.countryCode) &&
             (BodyData.countryName != null ? x.Countryname == BodyData.countryName) &&
             (BodyData.currencyCode != null ? x.Currencycode == BodyData.currencyCode) &&
             (BodyData.currencyCode != null ? x.Dialcode == BodyData.dialCode));
}

Answer 1

Straightforward way:

var CountryDataSet22 = CountryCodeDbContext.Countrydetails
    .Where(x => 
            (BodyData.countryCode  == null || x.Countrycode  == BodyData.countryCode)  &&
            (BodyData.countryName  == null || x.Countryname  == BodyData.countryName)  &&
            (BodyData.currencyCode == null || x.Currencycode == BodyData.currencyCode) &&
            (BodyData.dialCode     == null || x.Dialcode     == BodyData.dialCode)
    );

Or using extension:

public static class MyQueryableExtensions
{
    public static IQueryble<T> WhereIf<T>(this IQueryable<T> source, bool condiion, Expression<Func<T, bool> predicate)
    {
        if (condition)
            source = source.Where(predicate);
        return source;
    }
}

var CountryDataSet22 = CountryCodeDbContext.Countrydetails
    .WhereIf(BodyData.countryCode  != null, x => x.Countrycode  == BodyData.countryCode)
    .WhereIf(BodyData.countryName  != null, x => x.Countryname  == BodyData.countryName)
    .WhereIf(BodyData.currencyCode != null, x => x.currencyCode == BodyData.currencyCode)
    .WhereIf(BodyData.dialCode     != null, x => x.Dialcode     == BodyData.dialCode);