JoinTableAttribute Class

.NET Standard 2.x

Sets the joined table to be used in a model class. Multiple JoinTable attributes can be applied to one model class.

Namespace: SnapObjects.Data

Assembly: SnapObjects.Data.dll

Inherited Constructor

System.ComponentModel.DataAnnotations.Schema.TableAttribute

Syntax

   [AttributeUsage(AttributeTargets.Class | AttributeTargets.Struct, AllowMultiple = true)]
   public class JoinTableAttribute : TableAttribute, IJoinTable

Constructors

Name	Description
JoinTableAttribute(string name)	Initializes a new instance of the JoinTableAttribute class.
JoinTableAttribute(string alias, string name)	Initializes a new instance of the JoinTableAttribute class.

Properties

Name	Return Type	Description
Alias	string	Gets the alias of the joined table.
AliasDefined	bool	Gets whether the joined table has an alias or not.
JoinType	SqlJoinType	Gets or sets the type of join operation to be used in the FROM clause.
Name	String	Gets the name of the table to join.
OnRaw	string	Gets or sets the raw SQL condition from which the join is based.
Schema	String	Gets or sets the schema of the table to join.

Remarks

The JoinTable attribute is equivalent to applying the join type (INNER JOIN, FULL OUTER JOIN, LEFT OUTER JOIN, RIGHT OUTER JOIN, etc.) of the SQL Select statement to the model so as to define the joining relationship between tables.

Examples

Example 1

The following code example demonstrates how to use the constructor: JoinTable (name, Propreties: Schema, JoinType, OnRaw) to apply the JoinTable attribute to CourseJoinTable class. It uses LEFT JOIN to join Course table with StudentGrade table, and specifies the raw SQL search condition "Course.CourseID = StudentGrade.CourseID" on which the join is based.

Model: CourseJoinTable

using SnapObjects.Data;
using System;

namespace Appeon.ApiDoc.Models.School
{
    /// <summary>
    /// This model class maps to the dbo.Course and dbo.StudentGrade tables.
    /// </summary>
    [FromTable("Course", Schema = "dbo")]
    [JoinTable("StudentGrade", Schema = "dbo", JoinType =SqlJoinType.Left,
        OnRaw = "Course.CourseID = StudentGrade.CourseID")]
    public class CourseJoinTable
    {
        public int CourseID { get; set; }

        public string Title { get; set; }

        [SqlColumn("StudentGrade", column: "Grade")]
        public decimal? Grade { get; set; }

    }
}

Example Method: Example1

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

namespace Appeon.ApiDoc.JoinTableAttributeExamples
{
    public class JoinTableAttributeExample
    {
        private SchoolContext _context;

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

        public void Example1()
        {
            // Gets the SQL statement.
            string sql = ModelSqlBuilder.
                GetBuilder<CourseJoinTable>(_context).QuerySql;

            Console.WriteLine("SQL statement:");
            Console.WriteLine(sql);

            // Executes the SQL by a SqlExecutor object. 
            var resultSet = _context.SqlExecutor.Select<CourseJoinTable>(sql);

            /* This code example produces the following output:
            
            SQL statement:
            SELECT
             [dbo].[Course].[CourseID],
            [dbo].[Course].[Title],
            [StudentGrade].[Grade]
            FROM [dbo].[Course]
            LEFT JOIN [dbo].[StudentGrade]
            ON [Course].[CourseID] = [StudentGrade].[CourseID]
            */
        }
    }
}

Example 2

The following code example demonstrates how to use the constructor: JoinTable (alias, name, Propreties: Schema, JoinType, OnRaw) to apply the JoinTable attribute to CourseJoinTable2 class. It specifies an alias for the StudentGrade table.

Model: CourseJoinTable2

using SnapObjects.Data;
using System;

namespace Appeon.ApiDoc.Models.School
{
    /// <summary>
    /// This model class maps to the dbo.Course and dbo.StudentGrade tables.
    /// </summary>
    [FromTable("Course", Schema = "dbo")]
    [JoinTable("s", "StudentGrade", Schema = "dbo", JoinType = SqlJoinType.Left,
        OnRaw = "Course.CourseID = s.CourseID")]
    public class CourseJoinTable2
    {
        public int CourseID { get; set; }

        public string Title { get; set; }

        [SqlColumn("s", column: "Grade")]
        public decimal? Grade { get; set; }

    }
}

Example Method: Example2

        public void Example2()
        {
            // Gets the SQL statement.
            string sql = ModelSqlBuilder.GetBuilder<CourseJoinTable2>(_context).QuerySql;

            Console.WriteLine("SQL statement:");
            Console.WriteLine(sql);

            // Executes the SQL by a SqlExecutor object. 
            var resultSet = _context.SqlExecutor.Select<CourseJoinTable2>(sql);

            /* This code example produces the following output:
            
            SQL statement:
            SELECT
             [dbo].[Course].[CourseID],
            [dbo].[Course].[Title],
            [s].[Grade]
            FROM [dbo].[Course]
            LEFT JOIN [dbo].[StudentGrade] AS [s]
            ON [Course].[CourseID] = [s].[CourseID]
            */
        }

Applies to

.NET Standard

2.x