DwKeyModificationAttribute Class

.NET Standard 2.x

Specifies which SQL statement will be generated when the primary key changes, corresponding to the Key Modification defined by DataWindow.sqlStrategy.

Namespace: DWNet.Data

Assembly: DWNet.Data.dll

Inheritance Constructor

System.Attribute

Syntax

    [AttributeUsage(AttributeTargets.Class, AllowMultiple = false)]
    public class DwKeyModificationStrategyAttribute : Attribute

Constructors

Name	Description
DwKeyModificationStrategyAttribute(UpdateSqlStrategy sqlStrategy)	Initializes a new instance of the KeyModificationAttribute class.

Properties

Name	Return Type	Description
SqlStrategy	UpdateSqlStrategy	Which SQL statement to be generated when the primary key changes.

Remarks

The options are:

DeleteThenInsert: Deletes the current row and then inserts a new row.

Update: Directly updates the current row.

Examples

The following code example demonstrates how to use the Model DwKeyModificationStrategy attribute. The example defines DwKeyModificationStrategy which uses the UpdateSqlStrategy.DeleteThenInsert parameter, which means two SQL statements will be generated when updating the primary key, one is the Delete statement for deleting data, the other is the Insert statement for inserting new data.

Model: D_Onlinecourse_Modifiykey

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_onlinecourse_modifiykey", DwStyle.Grid)]
    [Table("OnlineCourse")]
    #region DwSelectAttribute  
    [DwSelect("PBSELECT( VERSION(400) TABLE(NAME=\"OnlineCourse\" ) @(_COLUMNS_PLACEHOLDER_) )")]
    #endregion
    [DwKeyModificationStrategy(UpdateSqlStrategy.DeleteThenInsert)]
    [UpdateWhereStrategy(UpdateWhereStrategy.KeyColumns)]
    public class D_Onlinecourse_Modifiykey
    {
        [Key]
        [DwColumn("OnlineCourse", "CourseID")]
        public int Courseid { get; set; }

        [StringLength(100)]
        [DwColumn("OnlineCourse", "URL")]
        public string Url { get; set; }

    }

}

Example Method:

using System;
using DWNet.Data;

namespace Appeon.ApiDoc.DwKeyModificationStrategyAttributeExamples
{
    public class DwKeyModificationStrategyAttributeExample
    {
        private readonly SchoolContext _context;

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

        public void Example()
        {
            var datastore = new DataStore("d_onlinecourse_modifiykey", _context);
            datastore.Retrieve();

            //Sets the Courseid in the first row to 1045.
            datastore.SetItem(0, "Courseid", 1045);
            
			//Commits modifications to the DataStore.
			datastore.Update();

            /* The following SQL is generated:
            
            exec sp_executesql N'DELETE FROM [OnlineCourse] 
            WHERE [CourseID] = @p_p0;
            SELECT @@ROWCOUNT;

            ',N'@p_p0 int',@p_p0=2021

            exec sp_executesql N'INSERT INTO [OnlineCourse] ([CourseID], [URL])
            VALUES (@pp0, @pp1);
            SELECT @@ROWCOUNT;

            ',N'@pp0 int,@pp1 nvarchar(4000)',@pp0=1045,@pp1=N'http://www.fineartschool.net/Composition'
            */
        }
    }
}

Example Refer To

DataWindow File: d_onlinecourse_modifiykey