DwComputeAttribute Class

.NET Standard 2.x

Specifies the computed column.

Namespace: DWNet.Data

Assembly: DWNet.Data.dll

Inheritance Constructor

System.Attribute

Syntax

 [AttributeUsage(AttributeTargets.Property, AllowMultiple = false)]
 public class DwComputeAttribute : PropertySaveAttribute

Constructors

Name	Description
DwComputeAttribute(string expression)	Initializes a new instance of the DwComputeAttribute class.

Properties

Name	Return Type	Description
Expression	string	Computed column expression.

Remarks

Corresponding to the computed column defined by DataWindow.

Examples

The following code example demonstrates how to use the Model DwCompute attribute to define a computed column, and get the value of this computed column.

Model: D_Person_With_Dwcompute

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using SnapObjects.Data;
using DWNet.Data;
using Newtonsoft.Json;
using System.Collections;

namespace Appeon.ApiDoc.Models
{
    [DataWindow("d_person_with_dwcompute", DwStyle.Grid)]
    [Table("Person")]
    #region DwSelectAttribute  
    [DwSelect("PBSELECT( VERSION(400) TABLE(NAME=\"Person\" ) @(_COLUMNS_PLACEHOLDER_) )")]
    #endregion
    [DwKeyModificationStrategy(UpdateSqlStrategy.DeleteThenInsert)]
    [UpdateWhereStrategy(UpdateWhereStrategy.KeyAndConcurrencyCheckColumns)]
    public class D_Person_With_Dwcompute
    {
        [Key]
        [Identity]
        [DwColumn("Person", "PersonID")]
        public int Personid { get; set; }

        [ConcurrencyCheck]
        [StringLength(50)]
        [DwColumn("Person", "LastName")]
        public string Lastname { get; set; }

        [ConcurrencyCheck]
        [StringLength(50)]
        [DwColumn("Person", "FirstName")]
        public string Firstname { get; set; }

        [JsonIgnore]
        [DwCompute("firstname + \" \" + lastname")]
        public object Compute_Fullname { get; set; }

    }

}

Example Method:

using System;
using DWNet.Data;

namespace Appeon.ApiDoc.DwComputeAttributeExamples
{
    public class DwComputeAttributeExample
    {
        private readonly SchoolContext _context;

        public DwComputeAttributeExample(SchoolContext dataContext)
        {
            // Sets the data context.
            _context = dataContext;
        }

        public void Example()
        {
            var datastore = new DataStore("d_person_with_dwcompute", _context);
            datastore.Retrieve();
			
			//Gets the full name by the computed column in the first row.
            string fullName = datastore.GetItem<string>(0, "Compute_Fullname");

            // Shows the value of the computed column.
            Console.WriteLine($"fullName={fullName}.");

            /* This code example produces the following output:
            
            fullName=Kim Abercrombie.
            */
        }
    }
}

Example Refer To

DataWindow File: D_Person_With_Dwcompute