IQueryAndOrBuilder<TModel>.AndWhereIsNull(string left) Method

.NET Standard 2.x

Adds the AND logical operator and a search condition to the WHERE clause; and uses IS NULL operator to search for values that are null.

Namespace: SnapObjects.Data

Assembly: SnapObjects.Data.dll

Syntax

  IQueryAndOrBuilder<TModel> AndWhereIsNull(string left);

Parameters

left System.String

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

Returns

IQueryAndOrBuilder<TModel>

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

Examples

The following code example demonstrates how to use the AndWhereIsNull method to add an AND IS NULL condition to the WHERE clause. In this example, the IS NULL condition specifies that the HireDate value must be null.

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

namespace Appeon.ApiDoc.IQueryAndOrBuilderExamples
{
    public class AndWhereIsNullExample
    {
        private SchoolContext _context;
        
        public AndWhereIsNullExample(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("EnrollmentDate")
                   .AndWhereIsNull("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:    1001
                FirstName:   Chen
                LastName:    Jack
                HireDate:
                EnrollmentDate:
                Discriminator:   boy
            */
        }
    }
}

Example Refer To

Model Class: Person

Applies to

.NET Standard

2.x