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Validation Controls In Asp.Net

In this article we will discuss about validation controls in asp.net. Validation means to confirm whether an input from the user contains the permissible values or not.

ASP.NET provides following validation controls

RequiredFieldValidator
RangeValidator
CompareValidator
RegularExpressionValidator
ValidationSummary
CustomValidator

Let us discuss each validation control one by one.

Requiredfieldvalidator

RequiredFieldValidator control ensures that the control should contain some value.

Syntax

Click to Enlarge

Properties

Property	Description
ID	Unique identifier for RequiredFieldValidator control.
ControlToValidate	ID of the control whose value is checked by validation control
ErrorMessage	What will be the error message displayed when the control is empty.

Example

<asp:TextBox ID="txtName" runat="server"></asp:TextBox>
<asp:RequiredFieldValidator ID="rfvName" ControlToValidate="txtName" 
        ErrorMessage ="Please select value"
        runat="server"></asp:RequiredFieldValidator>
<asp:Button ID="btnClick" runat="server" Text="Click" />

Output

Click to Enlarge

Rangevalidator

RangeValidator ensures that the user input is within the specified range.

Syntax

Click to Enlarge

In the preceding image you could see that most of the properties are same as RequiredFieldValidator. But there are 3 additional properties as shown in following table

Property	Description
Type	Specifies the data type of user input.
MinimumValue	specifies the minimum value of user input
MaximumValue	specifies the maximum value of user input

Example

<asp:TextBox ID="txtName" runat="server"></asp:TextBox>
<asp:RangeValidator 
            ID="rvName" 
            ControlToValidate="txtName" 
            Type=" Integer "
            ErrorMessage ="Value out of range" 
            MinimumValue="0" 
            MaximumValue="5"
            runat="server"></asp:RangeValidator>
<asp:Button ID="btnClick" runat="server" Text="Click" />

Output

Click to Enlarge

Comparevalidator

CompareValidator is for comparing the value of one control with other or comparing the constant value with a control.

Syntax

Click to Enlarge

Property	Description
Type	Specifies the data type of user input.
ControlToCompare	One of the 2 controls which need to be compared.
ValueToCompare	It specifies the constant value to compare with.
Operator	Specifies the comparison operator

Example

<asp:TextBox ID="txtName" runat="server"></asp:TextBox>
<asp:TextBox ID="txtName2" runat="server"></asp:TextBox>
<asp:CompareValidator 
            ID="rvName" 
            ControlToValidate="txtName" 
            Type="Integer"
            ControlToCompare="txtName2"
            Operator="Equal"
            ErrorMessage ="Values are not equal" 
            runat="server"></asp:CompareValidator>
<asp:Button ID="btnClick" runat="server" Text="Click" />

Output

Click to Enlarge

If you want to compare constant value then you can use ValueToCompare attribute instead of ControlToCompare.

<asp:TextBox ID="txtName" runat="server"></asp:TextBox>
<asp:CompareValidator 
            ID="rvName" 
            ControlToValidate="txtName" 
            Type="Integer"
            ValueToCompare="5"
            Operator="Equal"
            ErrorMessage ="Values are not equal" 
            runat="server"></asp:CompareValidator>
<asp:Button ID="btnClick" runat="server" Text="Click" />

Picture showing the output of comparevalidator with ValueToCompare attribute in asp.net

Click to Enlarge

Regularexpressionvalidator

The RegularExpressionValidator allows validating the input text by matching against a pattern of a regular expression

Syntax

Click to Enlarge

Property	Description
ValidationExpression	Specifies the regular expression

Example

Enter 10 digit mobile number
        
<asp:TextBox ID="txtMobileNumber" runat="server"></asp:TextBox>
<asp:RegularExpressionValidator id="reMobileNumber" 
                     ControlToValidate="txtMobileNumber"
                     ValidationExpression="\d{10}"
                     ErrorMessage="Mobile number must be 10 numeric digits"
                     runat="server"/>
<asp:Button ID="btnClick" runat="server" Text="Click" />

Output

Click to Enlarge

Validationsummary

ValidationSummary doesn’t do any validation. The purpose of ValidationSummary is to show the summary of all errors on the web page. Let us work on the preceding example i.e. RegularExpressionValidator and see how to use ValidationSummary.

<div>
	<asp:ValidationSummary ID="ValidationSummary1" runat="server"/>
	<br />

        Enter 10 digit mobile number
        
	<asp:TextBox ID="txtMobileNumber" runat="server"></asp:TextBox>
	<asp:RegularExpressionValidator ID="reMobileNumber" ControlToValidate="txtMobileNumber"
            ValidationExpression="\d{10}" ErrorMessage="Mobile number must be 10 numeric digits"
            runat="server" />
	<asp:Button ID="btnClick" runat="server" Text="Click" />
</div>

In the preceding code I have added validation summary. Now run the application.

Picture showing the output of validationsummary in asp.net

Click to Enlarge

As you can see in the preceding image validation summary is displayed as bulleted points.

Customvalidator

If all the validators that are specified in the preceding sections are not satisfying your requirements and it is required to write custom validation logic then you can use CustomValidator. You can validate client side as well as server side using CustomValidator

Syntax

Click to Enlarge

Example

<asp:ValidationSummary ID="ValidationSummary1" runat="server"/>
<br />

        Enter 10 digit mobile number
        
<asp:TextBox ID="txtMobileNumber" runat="server"></asp:TextBox>
<asp:CustomValidator ID="cvMobileNumber" OnServerValidate="cvMobileNumber_Validate"
        ErrorMessage = "Please enter the mobile number" Display="None"
            runat="server"  />
<asp:Button ID="btnClick" runat="server" Text="Click" />

In the preceding code CustomValidator is checking if textbox contains any value or not. Although this can be done using RequiredFieldValidator as well. But the main purpose here to show the implementation.

Code behind is

protected void cvMobileNumber_Validate(object sender, ServerValidateEventArgs e) {
  if (string.IsNullOrWhiteSpace(txtMobileNumber.Text)) {
    e.IsValid = false;
  }
}

Output

Click to Enlarge

You can also use JavaScript in CustomValidator

<asp:ValidationSummary ID="ValidationSummary1"  EnableClientScript="true"
        runat="server" />
<br />

        Enter 10 digit mobile number
        
<asp:TextBox ID="txtMobileNumber" runat="server"></asp:TextBox>
<asp:CustomValidator ID="cvMobileNumber" ClientValidationFunction = "validate" 
        ErrorMessage = "Please enter the mobile number" Display="None"
            runat="server"  />
<asp:Button ID="btnClick" runat="server" Text="Click" />

JavaScript code is

  <script type="text/javascript">
 function validate(val, args) {
    if (document.getElementById('<%=txtMobileNumber.ClientID %>').value == "") {
        args.IsValid = false;
    }
}
</script>

When you run the application you see the output that we saw in the preceding image.

Posted By -	Karan Gupta

Posted On -	Tuesday, May 12, 2015

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