FromTableAttribute Class

.NET Standard 2.x

Specifies the database table that a model class is mapped to. Multiple FromTable 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 FromTableAttribute : TableAttribute, IFromTable

Constructors

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

Properties

Name	Return Type	Description
Alias	string	Gets the alias of the specified database table.
AliasDefined	bool	Gets whether the specified database table has an alias or not.
Name	String	Gets the name of the table.
Schema	String	Gets or sets the schema of the table.
WhereRaw	string	Gets or sets the raw WHERE clause for the specified database table.

Remarks

The FromTable attribute is equivalent to the database table specified in the FROM clause of the SQL SELECT statement. One or more FromTable attributes can be applied to one model class in order to retrieve data from one or more database tables in one model.

When no Table attribute is applied, and one or more FromTable attributes are being applied to a model class, the first FromTable attribute denotes the only one database table that the model class should use when executing the SQL DML.

Examples

Example 1

The following code example demonstrates how to use the constructor: FromTable (name, Propreties: Schema, WhereRaw) to apply the FromTable attribute to the PersonFromTable class.

Model: PersonFromTable

using SnapObjects.Data;
using System;

namespace Appeon.ApiDoc.Models.School
{
    /// <summary>
    /// This model class maps to the dbo.Person table.
    /// </summary>
    [FromTable("Person", Schema = "dbo", WhereRaw = "PersonID < 10")]    
    public class PersonFromTable
    {      
        public int PersonID { get; set; }

        public string LastName { get; set; }

        public string FirstName { get; set; }

        public DateTime? HireDate { get; set; }

        public DateTime? EnrollmentDate { get; set; }

        public string Discriminator { get; set; }

    }
}

Example Method: Example1

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

namespace Appeon.ApiDoc.FromTableAttributeExamples
{
    public class FromTableAttributeExample
    {
        private SchoolContext _context;

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

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

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

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

            /* This code example produces the following output:
            
            SQL statement:
            SELECT
             [PersonID],
            [LastName],
            [FirstName],
            [HireDate],
            [EnrollmentDate],
            [Discriminator]
            FROM [dbo].[Person]
            WHERE ([PersonID] < 10)
            */
        }
    }
}

Example 2

The following code example demonstrates how to use the constructor: FromTable (alias, name, Propreties: Schema, WhereRaw) to apply the FromTable attribute to the PersonFromTable2 class. It specfies the raw WHERE clause using the WhereRaw parameter.

Model: PersonFromTable2

using SnapObjects.Data;
using System;

namespace Appeon.ApiDoc.Models.School
{
    /// <summary>
    /// This model class maps to the dbo.Person table.
    /// </summary>
    [FromTable("p", "Person", Schema = "dbo", WhereRaw = "PersonID < 10")]
    public class PersonFromTable2
    {
        public int PersonID { get; set; }

        [SqlColumn(tableAlias: "p", column: "LastName")]        
        public string PersonLastName { get; set; }

        public string FirstName { get; set; }

        public DateTime? HireDate { get; set; }

        public DateTime? EnrollmentDate { get; set; }

        public string Discriminator { get; set; }

    }
}

Example Method: Example2

        public void Example2()
        {
            // Gets the SQL statement.
            string sql = ModelSqlBuilder.GetBuilder<PersonFromTable2>(_context).QuerySql;

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

            // Executes the SQL by a SqlExecutor object. 
            var persons = _context.SqlExecutor.Select<PersonFromTable2>(sql);

            /* This code example produces the following output:
            
            SQL statement:
            SELECT
             [PersonID],
            [p].[LastName],
            [FirstName],
            [HireDate],
            [EnrollmentDate],
            [Discriminator]
            FROM [dbo].[Person] AS [p]
            WHERE ([PersonID] < 10)
            */
        }

Applies to

.NET Standard

2.x