ISqlExecutor.SelectLazy<TModel>(string sqlText, params object[] parameters) Method
.NET Standard 2.x | Current Version (1.0.1) 
Executes the SQL SELECT statement and returns an IEnumerable <TModel> object that can be used to load the result set lazily.
Namespace: SnapObjects.Data
Assembly: SnapObjects.Data.dll
Syntax
public IEnumerable<TModel> SelectLazy<TModel>(string sqlText, params object[] parameters);
Type Parameters
TModel
The datatype of the model object which represents the data row in the result set.
You can also specify DynamicModel to TModel if you do not want to define a custom model class.
Parameters
sqlText System.String
A raw SQL Statement which contains the parameter placeholders.
The proper syntax of a parameter placeholder is specific to the data source (e.g.: @newFirstName for SQL Server). To make a parameterized SQL ( e.g: update Person set FirstName = @newFirstName where PersonId = 1), these placeholders are filled in with the actual parameter values when the SQL statement is executed.
parameters System.Object[]
(Optional) One or more ParamValue objects which contain the values corresponding to the SQL parameter identifier names.
You can also pass the arguments directly in the order in which each parameter identifier name appears in sqlText for the first time, without using the ParamValue object.
Returns
System.Collections.Generic.IEnumerable<TModel>
Returns an IEunmerable<TModel> object which can load the result set lazily.
Remarks
This method uses command behavior of CommandBehavior.SequentialAccess internally, which provides a way for the DataReader to handle rows that contain columns with large binary values.
It creates each model object and reads data from database to this model object only when the data is asked for. You can use this method to save resources and improve performance by deferring the initialization of expensive objects until they are requested.
You have to open the current connection (DataContext.CurrentConnection property) explicitly before calling this method and close the connection explicitly after calling this method.
Examples
The following code example demonstrates how to use the SelectLazy<TModel>(String, params object[]) method to execute the SQL statement lazily.
using SnapObjects.Data;
using System;
namespace Appeon.ApiDoc.ISqlExecutorExamples
{
public class SelectLazyExample
{
private readonly SchoolContext _context;
public SelectLazyExample(SchoolContext dataContext)
{
// Sets the data context
_context = dataContext;
}
public void Example1()
{
// Defines the SQL statement.
var sql = @"SELECT CourseID, Title
FROM Course
WHERE CourseID = @Courseid";
// Opens the current connection.
_context.CurrentConnection.Open();
// Executes the SQL statement.
// It dosen't get the result set from database eagerly.
// This method is usually used to handle rows that contain columns
// with large binary values.
var result = _context.SqlExecutor.SelectLazy<DynamicModel>(sql, 2030);
// Gets each row of the result set from database one by one.
// It creates each model object and reads data from database to
// this model object only when the data is asked for.
foreach (var model in result)
{
Console.WriteLine("Title: {0}.", model.GetValue(1));
}
// Closes the current connection.
_context.CurrentConnection.Close();
/*This code produces the following output:
Title: Poetry.
*/
}
}
}
Applies to
.NET Standard
2.x