IQueryWhereBuilder.WhereIsNull(string left) Method

.NET Standard 2.x

Creates a WHERE clause, and adds a search condition to the WHERE clause. Uses IS NULL operator to search for values that are null.

Namespace: SnapObjects.Data

Assembly: SnapObjects.Data.dll

Syntax

  IQueryAndOrBuilder<TModel> WhereIsNull(string left);

Parameters

left System.String

A SQL expression on the left of the IS NULL operator.

Returns

IQueryAndOrBuilder<TModel>

Returns an IQueryAndOrBuilder<TModel> object which can be used to add more search conditions to the current WHERE clause.

Examples

The following code example uses the WhereIsNull method to specify that data retrieved from the "Person" table must have a null value for HireDate.

using Appeon.ApiDoc.Models.School;
using SnapObjects.Data;
using System;
using System.Threading.Tasks;

namespace Appeon.ApiDoc.IQueryWhereBuilderExamples
{
    public class WhereIsNullExample
    {
        private SchoolContext _context;
        
        public WhereIsNullExample(SchoolContext dataContext)
        {
            // Sets Data Context
            _context = dataContext;
        }

        public async Task<int> Example()
        {
            // Get a QueryBuilder.
            var Builder = _context.SqlModelMapper.GetQueryBuilder<Person>();
            
            // Defines a WHERE condition that the column of HireDate is empty.
            Builder.WhereIsNull("HireDate");
            
            var result = (await Builder.LoadAsync()).FirstOrDefault();
            
            if (result != null)
            {
                Console.WriteLine("PersonID:    {0}", result.PersonID);
                Console.WriteLine("FirstName:   {0}", result.FirstName);
                Console.WriteLine("LastName:    {0}", result.LastName);
                Console.WriteLine("HireDate:    {0}", result.HireDate);
                Console.WriteLine("EnrollmentDate:  {0}", result.EnrollmentDate);
                Console.WriteLine("Discriminator:   {0}", result.Discriminator);
                
                return result.PersonID;
            }
            else
            {
                Console.WriteLine("Not found!");
                
                return 0;
            }
            
            /*This code example produces the following output:   
            
                PersonID:    2
                FirstName:   Gytis
                LastName:    Barzdukas
                HireDate:
                EnrollmentDate:  9/1/2005 12:00:00 AM
                Discriminator:   Student
            */
        }
    }
}

Example Refer To

Model Class: Person

Applies to

.NET Standard

2.x