Working with validators

In any application, validating the user input is very important; it is process of the identifying what is incorrect in the user inputs. It is used to identify the errors in the user input before carrying out the business process.

Take for example; we are going to create a new email-using Yahoo. Where in the user id has to be given before submitting the form. This is one kind of validation. There are several other cases like the password should not exceed 10 characters or Date of birth entered should not exceed the current date or the age should be in the between a range say (10 to 50 or above 10 etc) or even the format in which the data are given.

Validators in ASP.NET

In this article lets discuss about the validators and its kinds in ASP.Net.

There are five different kinds of validators available in .net, they are as follows,

• Required Field validators
• Compare Validators
• Range Validators
• RegularExpression validators
• Custom Validators

Let us first see what each validators is meant for.

Required Field Validators

The name itself describes it, yes it is the validator used to check whether the user has entered/selected a value or not.

[code]

<asp:RequiredFieldValidator id="valReq" runat="server" ControlToValidate=”"

    ErrorMessage="* You must enter a value" Display="dynamic">

</asp:RequiredFieldValidator>

[/code]

Compare Validators

In some case we may have to do a validation based on some of the underlying values/control data, for example.,

Now we need to check whether the Password and Re-Enter password in the new user form are the same. In these cases compare validators can be used.

[code]

<asp:CompareValidator id="valCom" runat="server"

    ControlToValidate="textbox1" ControlToCompare="textbox2"

    Operator="Equals"

    ErrorMessage=”"

    Display="dynamic">*

</asp:CompareValidator>[/code]  

Range Validator Control

In most of the case we may have to check whether the data entered is between a specified range. For example, the age should be minimum 10 and maximum 100.

In those cases range validators can be used.

[code]

<asp:RangeValidator id="valRange" runat="server"

    ControlToValidate="age"

    MaximumValue="100"

    MinimumValue="10"

    Type="integer"

    ErrorMessage=“* The age must be between 10 and 100″ Display=“static”></asp:RangeValidator> [/code] 

Regular Expression validator

It is one of important validators available in Asp.net it is used to compare the data entered against specific format. For example date has to be entered in dd/MM/yyyy format only.

[code]

<asp:RegularExpressionValidator id="valReg" runat="server"

    ControlToValidate=""

    ValidationExpression=""

    ErrorMessage=""

    display="dynamic">

</asp:RegularExpressionValidator>

[/code]

 
Custom Validators 

In all the cases the above validators cannot be used, that is some validations cannot be done on the page, it has to come for round trips to the server validate the data in the server against some condition or some data base values and then display error messages based on that.

For example, checking whether the user name already exists or not.

<asp:CustomValidator id="valCustom" runat="server"

    ControlToValidate="textbox1"

    ClientValidationFunction="ClientValidate"

    OnServerValidate="ServerValidate"

    ErrorMessage=" " dispaly="dynamic">*

</asp:CustomValidator>

We will see in depth of these validators in our next chapters.

Now lets see what are the attributes are methods available in common

 Common Properties and Methods of validators. 

ControlToValidate –

Take a string input, name of the control to be validated.

ErrorMessage

The error message that needs to be displayed in case if the validations fails (some error in the data)

IsValid

Returns true if the control has valid date, else returns false.

Validate

Method to validate the control against the validation rule and to update the Isvalid property.

Display

There are three different ways of presenting the data or error message to the user.

• None – Validation message will not be displayed at all
• Static – Allocate space on the page to display the error message.
• Dynamic – Space will not be allocated on the page if there is no error. Space will be dynamically added only when the validation fails.

Let me take a report sample and lets go step by step in creating the report.

Create the following data structure.

1. Student Table

2. Class Table

3. ClassSubjects Table

4. StudentMarks table

5. Exam table

Now lets see how we are going to design the report card for the students. Requirements are as follows,

·        Each student report should be printed in a different page

·        Should display the students mark details in the following format

Steps to create the report based on the above requirement. 

Step1: Create the excel template as shown below.

·        Create a black Excel document

·        Delete the Sheet2 and Sheet3

·        Select the cells A2 to G2 and Merge them

·        Do the remaining as shown in the above pic.

·        Select cells from A1 to G22, Select File menu è Print Area è Set Print Area

·        Print Area will be defined.

·        We are not going to write any data from sp in this section. This is the section were the data is going to displayed. Or this is the section that will be printed.

·        The remaining cells will be used to write the required data for the report they act as the report data source.

·        Lets define areas, where we are going to dump the data.

o       Select the cells J4 to M4

o       Insert è Name è Define (to define a new area)

o       “Define Name” dialog opens and name the region as “StudentInfo”

o       Similarly the cells J7 to K7 and name the region as “Marks”

o       We will be dumping the data in the regions only from the Stored procedure.

·        Lets see how we are going to set the data in the report print section

·        Printing the Header “Progress Report of the XXXXXXX exam – YYYY(Year)”

·        This should be achieved using the macro. Exam name and the Year of the exam should be obtained from the StudentInfo region

·        Lets define the Macro, Select “Tools è Macros è Visual Basic Editor” or press “ALT + F11”

·        VBA Window will open. Select the “Sheet1” node in the project explore, Right Click and Select “View Code”

·        Code window opens

·        Select “WorkSheet” object and select the Activate event.

·        Write the following code.

Cells(2, 1) = “Progress Report of the ” & Cells(5, 13) & ” - ” & Format(“YYYY”, Cells(5, 12))

·        We need to fill the Name, Exam Date, Class

·        Lets use the formula to fill these data

·        Select the cell “C4” in the formula bar type “=J5” and the select the cell c4, set the necessary format by right clicking on the cell and formatting the cell.

·        Now lets populates the marks.

o       Select the cell “B9” and in the formula type “=J9” repeat the same for other rows till “B14” assign each row with the corresponding J cells

o       Select the cell “C9” and in the formula type “=K9” repeat the same for the other rows till C14 assign each row with the corresponding K cells

o       Select the cell “D9” and in the formula type “=L9” repeat the same for the other rows till D14 assign each row with the corresponding L cells

o       Select the cell E16  and type the formula as “=SUM(E9:F13)” which will calculate the Total.

o       To print the grade lets create a macro.

If CInt(Cells(9, 12)) < 40 Or CInt(Cells(10, 12)) < 40 Or CInt(Cells(11, 12)) < 40 Or CInt(Cells(12, 13)) < 40 Or CInt(Cells(13, 13)) < 40 Then

    Cells(17, 5) = “F”

ElseIf CInt(Cells(16, 5)) > 400 Then

Cells(17, 5) = “O”

ElseIf CInt(Cells(16, 5)) > 300 Then

Cells(17, 5) = “A”

ElseIf CInt(Cells(16, 5)) > 200 Then

Cells(17, 5) = “B”

End If

·        Now we are all set with the report template

Step3: Create a page in ASP.NET as shown below.

Step3: populate the class drop down from the class table

Step4: populate the exam drop down from the exam table.

Step5: Next step is creating excel sheets (copy of the template created in step 1) for each student in the class, Also writing an sp which will dump the data in the excel sheets. The merge the excel sheet and display it as one excel sheet using java script.

This we will see in our next chapter.

Use the following SQL Script to generate the tables.

 if exists (select * from dbo.sysobjects where id = object_id(N’[dbo].[Class]‘) and OBJECTPROPERTY(id, N’IsUserTable’) = 1)
drop table [dbo].[Class]
GO

if exists (select * from dbo.sysobjects where id = object_id(N’[dbo].[ClassSubject]‘) and OBJECTPROPERTY(id, N’IsUserTable’) = 1)
drop table [dbo].[ClassSubject]
GO

if exists (select * from dbo.sysobjects where id = object_id(N’[dbo].[Exam]‘) and OBJECTPROPERTY(id, N’IsUserTable’) = 1)
drop table [dbo].[Exam]
GO

if exists (select * from dbo.sysobjects where id = object_id(N’[dbo].[Student]‘) and OBJECTPROPERTY(id, N’IsUserTable’) = 1)
drop table [dbo].[Student]
GO

if exists (select * from dbo.sysobjects where id = object_id(N’[dbo].[StudentMarks]‘) and OBJECTPROPERTY(id, N’IsUserTable’) = 1)
drop table [dbo].[StudentMarks]
GO

CREATE TABLE [dbo].[Class] (
 [ClassID] [bigint] IDENTITY (1, 1) NOT NULL ,
 [ClassName] [varchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL
) ON [PRIMARY]
GO

CREATE TABLE [dbo].[ClassSubject] (
 [SubjectID] [bigint] IDENTITY (1, 1) NOT NULL ,
 [ClassID] [bigint] NULL ,
 [SubjectName] [varchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
 [SubjectDesc] [varchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL
) ON [PRIMARY]
GO

CREATE TABLE [dbo].[Exam] (
 [ExamID] [bigint] IDENTITY (1, 1) NOT NULL ,
 [ExamTitle] [varchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NULL ,
 [ExamDate] [smalldatetime] NULL
) ON [PRIMARY]
GO

CREATE TABLE [dbo].[Student] (
 [StudID] [bigint] IDENTITY (1, 1) NOT NULL ,
 [FirstName] [varchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,
 [LastName] [varchar] (50) COLLATE SQL_Latin1_General_CP1_CI_AS NOT NULL ,
 [ClassID] [bigint] NOT NULL ,
 [Age] [int] NOT NULL
) ON [PRIMARY]
GO

CREATE TABLE [dbo].[StudentMarks] (
 [MarkID] [bigint] IDENTITY (1, 1) NOT NULL ,
 [StudID] [bigint] NOT NULL ,
 [SubjectID] [bigint] NOT NULL ,
 [Mark] [int] NOT NULL ,
 [ExamID] [bigint] NOT NULL
) ON [PRIMARY]
GO

ALTER TABLE [dbo].[Class] ADD
 CONSTRAINT [PK_Class] PRIMARY KEY  CLUSTERED
 (
  [ClassID]
 )  ON [PRIMARY]
GO

ALTER TABLE [dbo].[ClassSubject] ADD
 CONSTRAINT [PK_ClassSubject] PRIMARY KEY  CLUSTERED
 (
  [SubjectID]
 )  ON [PRIMARY]
GO

ALTER TABLE [dbo].[Exam] ADD
 CONSTRAINT [PK_Exam] PRIMARY KEY  CLUSTERED
 (
  [ExamID]
 )  ON [PRIMARY]
GO

ALTER TABLE [dbo].[Student] ADD
 CONSTRAINT [PK_Student] PRIMARY KEY  CLUSTERED
 (
  [StudID]
 )  ON [PRIMARY]
GO

ALTER TABLE [dbo].[StudentMarks] ADD
 CONSTRAINT [DF_StudentMarks_Mark] DEFAULT (0) FOR [Mark],
 CONSTRAINT [PK_StudentMarks] PRIMARY KEY  CLUSTERED
 (
  [MarkID]
 )  ON [PRIMARY]
GO