PasswordStrength

The PasswordStrength extender displays a visual indicator of password strength as the user types in a password field. It evaluates passwords against configurable character requirements (length, uppercase, lowercase, numbers, symbols) and displays feedback through text labels or a visual bar indicator.

Original Ajax Control Toolkit documentation: https://www.asp.net/ajax/ajaxcontroltoolkit/PasswordStrength

Features Supported in Blazor

• TargetControlID — ID of the password TextBox to monitor
• DisplayPosition — Where to show the strength indicator (RightSide, LeftSide, AboveRight, AboveLeft, BelowRight, BelowLeft)
• StrengthIndicatorType — Text labels or BarIndicator display
• PreferredPasswordLength — Target minimum length
• MinimumNumericCharacters — Required numeric characters
• MinimumSymbolCharacters — Required symbol characters
• MinimumUpperCaseCharacters — Required uppercase letters
• MinimumLowerCaseCharacters — Required lowercase letters
• RequiresUpperAndLowerCaseCharacters — Must contain both upper and lower
• TextStrengthDescriptions — Semicolon-delimited strength labels
• StrengthStyles — CSS classes for each strength level
• BarBorderCssClass — CSS class for bar indicator border
• TextCssClass — CSS class for text display
• HelpHandleCssClass — CSS class for help icon
• HelpHandlePosition — Where to show the help handle

DisplayPosition Enum

Controls where the indicator displays:

enum DisplayPosition
{
    RightSide = 0,
    LeftSide = 1,
    AboveRight = 2,
    AboveLeft = 3,
    BelowRight = 4,
    BelowLeft = 5
}

StrengthIndicatorType Enum

Controls the display style:

enum StrengthIndicatorType
{
    Text = 0,        // Text labels
    BarIndicator = 1 // Visual progress bar
}

Web Forms Syntax

<asp:TextBox ID="txtPassword" runat="server" TextMode="Password" />

<ajaxToolkit:PasswordStrength
    ID="pwd1"
    runat="server"
    TargetControlID="txtPassword"
    DisplayPosition="RightSide"
    StrengthIndicatorType="BarIndicator"
    PreferredPasswordLength="10"
    MinimumNumericCharacters="1"
    MinimumSymbolCharacters="1"
    MinimumUpperCaseCharacters="1"
    TextStrengthDescriptions="Very Poor;Weak;Average;Strong;Excellent" />

Blazor Migration

<TextBox ID="txtPassword" type="password" />

<PasswordStrength
    TargetControlID="txtPassword"
    DisplayPosition="DisplayPosition.RightSide"
    StrengthIndicatorType="StrengthIndicatorType.BarIndicator"
    PreferredPasswordLength="10"
    MinimumNumericCharacters="1"
    MinimumSymbolCharacters="1"
    MinimumUpperCaseCharacters="1"
    TextStrengthDescriptions="Very Poor;Weak;Average;Strong;Excellent" />

Migration is simple: Remove the ajaxToolkit: prefix and runat="server". Use enum type names for positions and indicator types!

Properties Reference

Property	Type	Default	Description
TargetControlID	string	(required)	ID of the password TextBox to monitor
DisplayPosition	DisplayPosition	RightSide	Where to display the strength indicator
StrengthIndicatorType	StrengthIndicatorType	Text	Text labels or BarIndicator display
PreferredPasswordLength	int	10	Target minimum password length
MinimumNumericCharacters	int	0	Minimum required numeric characters (0-9)
MinimumSymbolCharacters	int	0	Minimum required symbol characters
MinimumUpperCaseCharacters	int	0	Minimum required uppercase letters
MinimumLowerCaseCharacters	int	0	Minimum required lowercase letters
RequiresUpperAndLowerCaseCharacters	bool	false	Must contain both uppercase and lowercase
TextStrengthDescriptions	string	""	Semicolon-delimited strength labels (e.g., "Very Poor;Weak;Average;Strong;Excellent")
StrengthStyles	string	""	Semicolon-delimited CSS classes, one per strength level
BarBorderCssClass	string	""	CSS class for bar indicator border
TextCssClass	string	""	CSS class for text display element
HelpHandleCssClass	string	""	CSS class for help icon
HelpHandlePosition	DisplayPosition	RightSide	Where to display the help handle

Usage Examples

Basic Password Strength with Text

@rendermode InteractiveServer

<div>
    <label>Password:</label>
    <TextBox ID="txtPass" type="password" style="width: 200px;" />

    <PasswordStrength
        TargetControlID="txtPass"
        DisplayPosition="DisplayPosition.RightSide"
        StrengthIndicatorType="StrengthIndicatorType.Text"
        PreferredPasswordLength="8"
        MinimumNumericCharacters="1"
        TextStrengthDescriptions="Very Weak;Weak;Good;Strong;Very Strong" />
</div>

Password Strength with Bar Indicator

@rendermode InteractiveServer

<div>
    <label>New Password:</label>
    <TextBox ID="txtNewPassword" type="password" style="width: 250px;" />

    <PasswordStrength
        TargetControlID="txtNewPassword"
        DisplayPosition="DisplayPosition.BelowRight"
        StrengthIndicatorType="StrengthIndicatorType.BarIndicator"
        PreferredPasswordLength="12"
        MinimumNumericCharacters="1"
        MinimumSymbolCharacters="1"
        MinimumUpperCaseCharacters="1"
        MinimumLowerCaseCharacters="1"
        BarBorderCssClass="strength-bar-border"
        StrengthStyles="very-weak;weak;fair;good;excellent" />
</div>

<style>
    .strength-bar-border {
        border: 1px solid #ccc;
        height: 20px;
        margin-top: 5px;
        border-radius: 3px;
    }

    .very-weak { background-color: #d32f2f; }
    .weak { background-color: #f57c00; }
    .fair { background-color: #fbc02d; }
    .good { background-color: #689f38; }
    .excellent { background-color: #00796b; }
</style>

Strict Password Requirements

@rendermode InteractiveServer

<form>
    <div style="margin-bottom: 20px;">
        <label>Create Password (minimum 14 characters, mixed case, numbers, and symbols):</label>
        <TextBox ID="txtStrictPass" type="password" style="width: 300px;" />

        <PasswordStrength
            TargetControlID="txtStrictPass"
            DisplayPosition="DisplayPosition.BelowRight"
            StrengthIndicatorType="StrengthIndicatorType.BarIndicator"
            PreferredPasswordLength="14"
            MinimumNumericCharacters="2"
            MinimumSymbolCharacters="2"
            MinimumUpperCaseCharacters="1"
            MinimumLowerCaseCharacters="1"
            RequiresUpperAndLowerCaseCharacters="true"
            TextStrengthDescriptions="Insufficient;Weak;Fair;Good;Strong;Very Strong"
            StrengthStyles="strength-0;strength-1;strength-2;strength-3;strength-4;strength-5" />
    </div>

    <button type="submit" class="btn btn-primary">Register</button>
</form>

<style>
    .strength-0 { background-color: #d32f2f; width: 0%; }
    .strength-1 { background-color: #f57c00; width: 20%; }
    .strength-2 { background-color: #fbc02d; width: 40%; }
    .strength-3 { background-color: #abb52e; width: 60%; }
    .strength-4 { background-color: #7cb342; width: 80%; }
    .strength-5 { background-color: #00796b; width: 100%; }
</style>

Relaxed Password Requirements

@rendermode InteractiveServer

<TextBox ID="txtSimple" type="password" style="width: 200px;" />

<PasswordStrength
    TargetControlID="txtSimple"
    DisplayPosition="DisplayPosition.RightSide"
    StrengthIndicatorType="StrengthIndicatorType.Text"
    PreferredPasswordLength="6"
    TextStrengthDescriptions="Too Short;Weak;Fair;Good;Strong"
    TextCssClass="strength-label" />

<style>
    .strength-label {
        font-weight: bold;
        margin-left: 10px;
    }
</style>

HTML Output

The PasswordStrength extender produces a strength indicator element (typically a <div>) positioned near the password field, displaying either text labels or a visual bar.

JavaScript Interop

The PasswordStrength loads password-strength.js as an ES module. JavaScript handles:

• Monitoring password field input events
• Evaluating password against character requirements
• Calculating strength score based on weights
• Updating indicator display in real-time
• Managing text label visibility and styling
• Updating bar indicator width
• Positioning indicator relative to the password field

Render Mode Requirements

The PasswordStrength requires InteractiveServer render mode:

@rendermode InteractiveServer

Graceful Degradation

• SSR/Static mode: The extender silently skips initialization. Password field works normally without feedback.
• JavaScript disabled: Same as SSR — No strength indicator appears.

Migration Notes

From Web Forms Ajax Toolkit

1. Remove ajaxToolkit: prefix

   - <ajaxToolkit:PasswordStrength
   + <PasswordStrength
   

2. Remove runat="server" and ID attributes

3. Use enum types for positions and indicator types

   - DisplayPosition="RightSide"
   + DisplayPosition="DisplayPosition.RightSide"
   

Before (Web Forms)

<asp:TextBox ID="txtPassword" runat="server" TextMode="Password" />

<ajaxToolkit:PasswordStrength
    ID="pwd1"
    TargetControlID="txtPassword"
    DisplayPosition="RightSide"
    StrengthIndicatorType="BarIndicator"
    PreferredPasswordLength="8"
    MinimumNumericCharacters="1"
    TextStrengthDescriptions="Weak;Fair;Good;Strong"
    runat="server" />

After (Blazor)

<TextBox ID="txtPassword" type="password" />

<PasswordStrength
    TargetControlID="txtPassword"
    DisplayPosition="DisplayPosition.RightSide"
    StrengthIndicatorType="StrengthIndicatorType.BarIndicator"
    PreferredPasswordLength="8"
    MinimumNumericCharacters="1"
    TextStrengthDescriptions="Weak;Fair;Good;Strong" />

Best Practices

1. Balance security with usability — Don't require overly strict passwords that frustrate users
2. Show requirements upfront — Consider displaying password requirements above the field
3. Use BarIndicator for visual feedback — Bars are more intuitive than text for strength
4. Provide clear descriptions — Use labels like "Strong" vs "Very Strong" that users understand
5. Position wisely — Place indicator where it won't obscure other form fields
6. Test requirements — Verify your character rules are achievable and reasonable
7. Combine with validation — Use server-side validation in addition to client feedback

Troubleshooting

Issue	Solution
Indicator not appearing	Verify TargetControlID matches the TextBox's ID. Ensure @rendermode InteractiveServer is set.
Bar indicator not filling	Define StrengthStyles with CSS classes and ensure corresponding styles are in your stylesheet.
Descriptions not showing	If using StrengthIndicatorType.Text, provide TextStrengthDescriptions separated by semicolons.
Requirements too strict	Adjust PreferredPasswordLength and character requirements to match your security policy.
Indicator in wrong position	Use a different DisplayPosition value. Try AboveRight, BelowRight, or LeftSide.

See Also

• Ajax Control Toolkit Overview — How extenders work and render mode requirements
• TextBox Component — The TextBox control
• ValidatorCalloutExtender — Enhanced validation feedback
• Original Ajax Control Toolkit: https://www.asp.net/ajax/ajaxcontroltoolkit