How to Create CheckboxList in Asp.Net MVC

CheckboxList is used to provide some options to be select by the user. In this article we will create a list of items and then pass it to view to create a checkbox list.

Create two classes with the following format

public class CollectionVM
{
    public List<ChoiceViewModel> ChoicesVM { get; set; }
    public List<Int64> SelectedChoices { get; set; }
}

public class ChoiceViewModel
{
    public Int64 SNo { get; set; }
    public string Text { get; set; }
}

In controller’s action method write following code in which we will create a new list having some items created below. When we return this ViewModel in the view, we first set the SelectedChoices object to a new blank list of same type.

CollectionVM collectionVM = new CollectionVM();
List<ChoiceViewModel> choiceList = new List<ChoiceViewModel>();
choiceList.Add(new ChoiceViewModel() { SNo = 1, Text = "Objective Choice 1" });
choiceList.Add(new ChoiceViewModel() { SNo = 2, Text = "Objective Choice 2" });
choiceList.Add(new ChoiceViewModel() { SNo = 3, Text = "Objective Choice 3" });
choiceList.Add(new ChoiceViewModel() { SNo = 4, Text = "Objective Choice 4" });

collectionVM.ChoicesVM = choiceList;
collectionVM.SelectedChoices = new List<long>();
return View(collectionVM);

In View page start a loop to create individual checkbox and label for each item added above.

@using (Html.BeginForm())
{
    <div>
        <ul>
            @foreach (var choice in Model.ChoicesVM)
            {
                <li>
                    <input 
                                id="choice@(choice.SNo)"
                                type="checkbox" 
                                name="SelectedChoices"
                                value="@choice.SNo"
                                @(Model.SelectedChoices.Contains(choice.SNo) ? "checked" : "")/>
                    <label for="operator@(choice.SNo)">@choice.Text</label>
                </li>
            
            }
        </ul>
        <input type="submit" value="Submit" name="submitBtn" id="submitBtn" />
    </div>
}

Check out above very simple code through which we will set all the checked item's sNo in the object SelectedChoices we have sent by viewmodel. And in the second line, particular label have been designed for each checkbox.

Now what happen when we submit this form. Write the HttpPost method of same action having this Viewmodel as parameter like:

[HttpPost]
        public ActionResult Index(CollectionVM collectionVM)
        {

This collectionVM object have all the SNo's of checked items by user. So we have created a checkbox list and then access all the checked items in our controller's action.

Use Multiple models in single view

How to Use Multiple Models in View using ViewModel: Asp.Net MVC

Asp.Net MVC uses such type of classes in which each field may contains specific validation rules using data annotations, to let the user interact with those only. These fields may contains some extra fields to be used as a temporary purpose.

Create two classes in the Models folder named Student and Employee as written below:

public class Student
{
public string Name { get; set; }
public int Age { get; set; }
public string City { get; set; }
}
public class Employee
{
public int EmpId { get; set; }
public string EmpName { get; set; }
}

Create a folder in our solution named ViewModels and add a class named Student_EmployeeViewModel which will have the following code.

public class Student_EmployeeViewModel
{
public List<Student> Students { get; set; }
public List<Employee> Employees { get; set; }
}

Come to our Controller (Home controller) and add an Action (Student_Employee) which will be type of HttpGet. This action will have some lines of code as below which contains two list of student and employee and then assign them to the newly created object of Student_EmployeeViewModel.

public ActionResult Student_Employee()
{
List<Student> studentList = new List<Student>();
studentList.Add(new Student() { Name = "Student 1", Age = 24 });
studentList.Add(new Student() { Name = "Student 2", Age = 25 });
studentList.Add(new Student() { Name = "Student 3", Age = 23 });

List<Employee> empList = new List<Employee>();
empList.Add(new Employee() { EmpName = "Employee 1", EmpId = 101 });
empList.Add(new Employee() { EmpName = "Employee 2", EmpId = 102 });
empList.Add(new Employee() { EmpName = "Employee 3", EmpId = 103 });

Student_EmployeeViewModel vm = new Student_EmployeeViewModel();
vm.Students = studentList;
vm.Employees = empList;
return View(vm);
}

Create an empty view by right clicking on this action and then Add View dialog box as discussed earlier. Write the following code in this view which will have two list as defined in our ViewModel.

@model MvcApplication1.Models.Student_EmployeeViewModel

@{
    ViewBag.Title = "Student_Employee";
    Layout = "~/Views/Shared/_Layout.cshtml";
}

<h2>Students List</h2>

@foreach (var item in Model.Students)
{
    <option>@item.Name &nbsp;&nbsp; @item.Age</option>
}

<h2>Employees List</h2>

@foreach (var item in Model.Employees)
{
    <option>@item.EmpName &nbsp;&nbsp; @item.EmpId</option>
}

In the above code, we run two loops for each list of student and employee and display their name and age/id on the page.

Run this project and write the address of this action in the address bar, this will shows all the data of student as well as employees we have added in the action.

Create DropDownList in MVC
Create CheckboxList in MVC

How to Rename and Dropping a Table in SQL

You can rename a table whenever required. The sp_rename stored procedure is used to remaname table. Sp_rename can be used to rename any database object, such as a table,view, stored procedure, or function. The syntax of the sp_rename stored procedure is:
Sp_rename old_name, new_name
Where,

• Oldname is the current name of the object.
• Newname is the new name of the object.

The following SQL query renames the EmployeeLeave table:
Sp_rename [HumanResources.EmployeeLeave] ,
[HumanResources.EmployeeVacation]

You can also rename a table by right-clicking the Table folder under the Database folder in the Object Employer window and selecting the rename option from the shortcut menu. After a table is created, you may need to see the details of the table. Details of the table include the column names and the constraints. For this purpose, you can use the sp_help command.

Dropping a Table

At times, when a table is not required, you need to delete a table. A table can be deleted along with all the associated database objects, such as its index, triggers, constraints, and permissions. You can delete a table by using the DROP TABLE statement. The syntax of
DROP TABLE [ database_name . [ schema_name ]. ] table_name
Where,

• Database_name specifies the name of the database where th table is created.
• Schema_name specifies the name of the schema to which the table belongs.
• Table_name specifies the name of the table that needs to be dropped.

When a table is deleted, any other database object referenced by the table needs to be deleted explicitly. This should be done before deleting the table. This is because while deleting a table, if violations occur in the rule of referential integrity then an error occurs that restricts you from deleting the table. Therefore, if your table is referenced then you must delete the referenced table or the referenced constraint and then delete the table.

For example in the HumanResources schema, the Employee table contains EmployeeID as its primary key. The EmployeeLeave table under the same schema contains EmployeeID as its foreign key and is referenced with the EmployeeID column of the Employee table. Therefore, when you want to delete the Employee table, you first need to delete the EmployeeLeave table.

You can also delete a table by right-clicking the Tables folder under the Database folder in the Object Explorer window and selecting the Delete option from the shortcut menu.

Create table using partition scheme

Creating a Table by Using the Partition Scheme

After you create a partition function and a partition scheme, you need to create a table that will store the partition records. You can use the following statements for the same:
Create Table EmpPayHistPart
(
EmployeeID int,
RateChangeDate datetime,
Rate money,
PayFrequency tinyint,
ModifiedDate datetime
) ON RateChangDate (RateChangeDate)

In the preceding statement, the RateChangDate refers to the partition scheme that is applied to the RateChangeDate column. The records entered in the EmpPayHistPart table will be stored based on the condition specified in the partition function.

Modifying a Table

You need to modify tables when there is a requirement to add a new column, alter the data type of a column, or add or remove constraints on the existing columns. For example, Adventure Works stores the leave details of all the employees in the EmployeeLeave table. According to the requirements, you need to add another column named ApprovedBy in the table to store the name of the supervisor who approved the leave of the employee. To implement this change, you can use the ALTER TABLE statement.

The syntax of the ALTER TABLE statement is:
ALTER TABLE [database_name . [ schema_name ] .] table_name
(
ALTER COLUMN column_name
{
[NULL | NOT NULL ]
}
  |WITH {CHECK | NOCHECK }] ADD COLUMN <column_difinition>
{
ADD CONSTRAINT constraint_name constraint_type
Where,

• Database_name specifies the name of the database in which the table is created. Schema_name specifies the name of the schema to which the table belongs.
• Table_name is the name of the table that is to be altered. If the table is not in the current database, then the user needs to specify the database name and the schema name explicitly.
• ALTER COLUMN specifies the name of the altered column.
• ADD COLUMN spevifies the name of the column to be added,
• Column_definition specifies the new column definition.
• WITH CHECK|WITH NOCHECK specifies whether the existing data is to be checked for a newly added constraint or a re-enabled constraint.
• Constraint_name specifies the name of the constraint to be created and must follow the rules for the identifier.
• Constraint_type specifies the type of constraint.

The following SQL query adds a column called ApprovedBy to the EmployeeLeave table:
ALTER TABLE HumanResources.EmployeeLeave
ADD ApprovedBy VARCHAR(30) NOT NULL

In the preceding example, the ApprovedBy column is added that can store string values.
When modifying a table, you can drop a constraint when it is not required. You can perform the task by altering the table by using the ALTER TABLE statement. The syntax to drop a constraint is:
ALTER TABLE [database_name . [ schema_name ] . [ schema_name . ] table_name DROP CONSTRAINT constraint_name
Where,

• Database_name specifies the name of the database in which the table is created.
• Schema_name specifies the name of the schema to which the table belongs.
• Table_name specifies the name of the table that contains the constraint to be dropped.
• Constraint_name specifies the name of the constraint to be dropped.

The following statement drops the default constraint, chkDefLeave of the EmployeeLeave table:
ALTER TABLE HumanResources.EmployeeLeave DROP CONSTRAINT chkDefLeave
In the preceding statement, the chkDefLeave constraint is dropped from the EmployeeLeave table.

Partition function in sql

How to Create Partition Function for Particular Column: SQL

A partition function specifies how a table should be partitioned. It specifies the range of values on a particular column. Based on which the table is partitioned. For example, in the scenario of Adventure Works, you can partition the data based on years. The following statement creates a partition function for the same:

CREATE PARTITION FUNCTION RateChangDate, (datetime)
AS RANGE RIGHT FOR VALUES (‘1996-01-01’, ‘2000-01-01’, ‘2004-01-01’, ‘2008-01-01’)

The preceding query creates a partition function named RateChangDate. It specifies that the data pertaining to the change in the payment rate will be partitioned based on the year.

Creating a Partition Scheme

After setting the partition function, you need to create the partition scheme. A partition scheme associates a partition function with various filegroups resulting in the physical layout of the data. Therefore, before creating a partition scheme, you need to create filegroups.

To create partition filegroups, you need to perform the following steps:

• Expand the Database folder in the Object Explorer windows and right-click the AdventureWorks database.
• Select the Properties option from the short-cut menu to display the Database Properties – AdventureWorks window.
• Select the Filegroups folder from Select a page pane to display the list of all the filegroups in AdventureWorks.
• Click the Add button to add a filegroup. Specify the name of the filegroup in the Name text box as Old.
• Report Step 4 to add four more filegroups named First, Second, Third, and Fourth, as shown in the following figure.
  
  
• Select the Files folder from Select a page pane to display the list of all the files.
• Click the Add button and type the name of the file as OldFile in the Logical Name text box, and select Old from the Filegroup drop-down list.
• Report Step 7 to create four files names File1, File2, File3, File4, select filegroup as First, Second, Third, Fourth for the files.
• Click OK button to close the Database Properties – AdventoreWorks window.

Execute the following statements in the Microsoft SQL Server Management
CREATE PARTITION SCHEME RateChangDate
AS PARTITION RateChangDate
TO (Old, First, Second, Third, Fourth)


Create partitioned table in sql

How to Create Partitioned Table in SQL Server

When the volume of data in a table increases and it takes time to query the data, you can partition the tables and store different parts of the tables in multiple physical locations based on a range of values for a specific column. This helps in managing the data and improving the query performance.

Consider the example of a manufacturing organization. The details of inventory movements are stored in the InventoryIssue table. The table contains a large volume of data and the queries take a lot of time to execute thereby slowing the report generation process.

To improve the query performance, you can partition the table to divide the data based on a condition and store different parts of the data in different locations. The condition can be based on the date of transaction and you can save the data pertaining to five years at a location. After partitioning the table, data can be retrieved directly from a particular partition by mentioning the partition number in the query.

In the preceding example, the partitioned table were created after the database had already been designed. You can also create partitioned tables while designing the database and creating tables. You can plan to create a partitioned table when you know that the data to be stored in the table will be large. For example, if you are creating a database for a banking application and you know that the transaction details will be voluminous, you can create the transaction table s with partitions.

Partitioning a table is only allowed in Enterprise Edition of SQL Server. To create a partitioned table, perform the following tasks:

• Create a partition function.
• Create a partition scheme.
• Create a table by using the partition scheme.

For example, the AdventureWorks database stores the data of all the employees for the last 11 years. This data includes the personal details of the employees and their payment rates. Whenever there is a change in the payment rate of an employee, it is recorded in a separate record. However, this result in generation of large volume of data. This adversely affects the query performance.

To improve the query performance, the database developer needs to partition the table storing the changes in wage rate.

Create Rule and User-defined DataType

How to use LINQ Generation operators in ASP.NET

Introduction

The Generation operators help in creating a new sequence of values. The Generation operators are DefaultlfEmpty, Empty, Range, and Repeat. The DefaultlfEmpty clause replaces an empty collection with a default single collection. The Empty clause refers to an empty collection. The Range clause generates a collection that contains a sequence of numbers. The Repeat clause generates a collection that contains at least one repeated value.
The syntax of Range clause is:
For C#
public static IEnumerable<int> Range( int start, int count);
The Range clause throws an ArgumentOutOfRangeException exception if the count is less than 0, or if the start + or count -1 parameters are larger than the maximum value.
The syntax of the Empty clause is:
For C#
public static IEnumerable<T> Empty<T>();
The Empty clause caches a single empty sequence of the given type.

Lets take an simple example

<form id="form1" runat="server">
    <div>
    
        <asp:ListBox ID="ListBox1" runat="server" Height="254px" Width="153px">
        </asp:ListBox>
        <br />
        <asp:Button ID="Button1" runat="server" onclick="Button1_Click" 
            Text="odd and even " />
    
    </div>
    </form>
Code Behind 
protected void Button1_Click(object sender, EventArgs e)
    {
        var num = from n in Enumerable.Range(1, 20)
                  select new { Number = n, oddevennumber = n % 2 == 1 ? "odd" : "even" };
        foreach (var item in num)
        {
            ListBox1.Items.Add("The number is " + item.Number + item.oddevennumber);
            
        }
    }
Code Generate the following output