Extension methods are a great way to add functionality to existing .Net classes and we made some to make your life easier. Just include the "using Rock;" in your code. You should definitely review the full list in the Rock.ExtensionMethods class, but we've highlighted most of them here for your reference.

Boolean Extensions

Bit() returns a numeric 1 (if true) or 0 (if false).

ToYesNo() returns either "Yes" or "No".

ToTrueFalse() returns the string "True" or "False".

CheckBoxList Extensions

SetValues() sets the Selected property of each item to true for each given matching values.

Control Extensions

LoadControl() loads a user control using the constructor with the parameters specified.

RockBlock() gets the parent RockBlock.

ParentUpdatePanel() returns the parent update panel for the given control (or null if none is found).

ControlsOfTypeRecursive() gets all controls of Type recursively http://stackoverflow.com/questions/7362482/c-sharp-get-all-web-controls-on-page.

DateTime Extensions

Age() returns the age at the current date.

TotalMonths() returns the total months.

TotalYears() returns the total years.

ToElapsedString() returns a friendly elapsed time string.

ToRelativeDateString() returns a string in FB style relative format (x seconds ago, x minutes ago, about an hour ago, etc.), or if max days has already passed, in FB datetime format (February 13 at 11:28am or November 5, 2011 at 1:57pm).

ToJavascriptMilliseconds() converts the date to an Epoch of milliseconds since 1970/1/1.

ToMonthDayString() converts the date to a string containing month and day values (culture-specific).

Dictionary (liquid) Extension Methods

Update() adds a new key/value to dictionary or if key already exists will update existing value.

Dictionary Extension Methods

AddOrReplace<TKey, TValue>() adds or replaces an item in a Dictionary.

AddOrIgnore<TKey, TValue>() adds an item to a Dictionary if it doesn't already exist in Dictionary.

Enum Extensions

ConvertToString() converts the enum value to its string value.

GetDescription() gets the enum description.

ConvertToInt() converts to int.

ConvertToEnum() converts a string value to an enum value.

// Assuming you've got an enum such as:
    public enum Status
    {
        Success,
        Fail,
        EpicFail,
    }

    // elsewhere, you can get the enum if you've only got the string value:
    Status s = "Epic Fail".ConvertToEnum<status>();    // w00t!</status>

ConvertToEnumOrNull() converts to enum or null.

AsDelimited() concatenates the items.

AsGuidList() converts a List to List only returning items that could be converted to a guid.

AsIntegerList() converts a List to List only returning items that could be converted to an int.

Join() joins a dictionary of items.

Geography Extension  Methods

Coordinates() coordinates the specified geography.

HiddenField Extensions

ValueAsInt() values as int.

SetValue() sets the value.

IsZero() determines whether the specified hidden field is zero.

HTMLControl Extensions

AddCssClass() adds a CSS class name to an html control.

RemoveCssClass() removes a CSS class name from an html control.

IEntity Extensions

RemoveEntity() removes the entity.

IHasAttributes Extensions

LoadAttributes() loads the attributes.

SaveAttributeValues() saves the attribute values.

CopyAttributesFrom() copies the attributes.

DefinedValue() gets the Defined Value name associated with this id.

SetReadOnlyValue() sets the read only value.

BindToEnum() binds to enum.

BindToDefinedType() binds to the values of a definedType.

ListControl ddl = new ListControl();
ddl.BindToDefinedType( DefinedTypeCache.Read( myConfiguredDefinedTypeGuid ) );

SelectedValueAsInt() returns the Value as Int or null if Value is.

SelectedValueAsId() returns the value of the currently selected item. It will return NULL if either is selected.

SelectedValueAsEnum() selects the value as enum.

SelectedValueAsEnumOrNull() selects the value as enum or null.

SelectedValueAsGuid() selects the value as unique identifier.

Object Extensions

ToJson() converts object to JSON string.

GetPropertyValue() gets the property value.

ToStringSafe() safely ToString() this item, even if it's null.

lavaDebugInfo() returns an html representation of object that is available to Lava.

Route Extensions

AddPageRoute() adds the page route.

Stream Extension Methods

ReadBytesToEnd() reads entire stream and converts to byte array.

String Extensions

RemoveSpecialCharacters() removes special characters from strings.

SplitCase() splits a Camel or Pascal cased identifier into separate words.

SplitDelimitedValues() returns a string array that contains the substrings in this string that are delimited by any combination of whitespace, comma, semi-colon, or pipe characters.

GetListItems() returns a List of ListItems that contains the values/text in this string that are formatted as either 'value1,value2,value3,...' or 'value1^text1,value2^text2,value3^text3,...'

ReplaceCaseInsensitive() replaces every instance of oldValue (regardless of case) with the newValue.

ReplaceWhileExists() replaces every instance of oldValue with newValue. Will continue to replace values after each replace until the oldValue does not exist.

EscapeQuotes() adds escape character for quotes in a string.

Quoted() adds quotes around the specified string and escapes any quotes that are already in the string.

Left() returns the specified number of characters, starting at the left side of the string.

Truncate() truncates a string after a max length and adds ellipsis. Truncation will occur at first space prior to maxLength.

Pluralize() pluralizes the specified string.

Singularize() singularizes the specified string.

AsNumeric() removes any non-numeric characters.

AsBoolean() returns True for 'True', 'Yes', 'T', 'Y', '1' (case-insensitive).

AsBooleanOrNull() returns True for 'True', 'Yes', 'T', 'Y', '1' (case-insensitive), null for empty string/null.

AsInteger() attempts to convert string to integer. Returns 0 if unsuccessful.

AsIntegerOrNull() attempts to convert string to an integer. Returns null if unsuccessful.

AsGuid() attempts to convert string to Guid. Returns Guid.Empty if unsuccessful.

AsGuidOrNull() attempts to convert string to Guid. Returns null if unsuccessful.

IsEmpty() determines whether the specified unique identifier is Guid.Empty.

AsDecimal() attempts to convert string to decimal. Returns 0 if unsuccessful.

AsDecimalOrNull() attempts to convert string to decimal. Returns null if unsuccessful.

AsDouble() attempts to convert string to double. Returns 0 if unsuccessful.

AsDoubleOrNull() attempts to convert string to double. Returns null if unsuccessful.

AsDateTime() attempts to convert string to DateTime. Returns null if unsuccessful.

AsTimeSpan() attempts to convert string to TimeSpan. Returns null if unsuccessful.

ResolveMergeFields() uses DotLiquid to resolve any merge codes within the content using the values in the mergeObjects.

HasMergeFields() determines whether the specified content has merge fields.

FormatAsHtmlTitle() converts string to a HTML title "first-word rest of string".

ConvertCrLfToHtmlBr() converts CR (carriage return) LF (line feed) to non-encoded html breaks (br).

ConvertBrToCrLf() converts the HTML br to cr lf.

EncodeHtml() HTML encodes the string.

SanitizeHtml() sanitizes the HTML by removing tags. If strict is true, all html tags will be removed; if false, only a blacklist of specific XSS dangerous tags and attribute values are removed.

ScrubHtmlAndConvertCrLfToBr() scrubs any html from the string but converts carriage returns into html suitable for web display.

IsValidEmail() returns true if the given string is a valid email address.

AsType() converts the value to Type, or if unsuccessful, returns the default value of Type.

Masked() masks the specified value if greater than 4 characters (such as a credit card number). For example, the return string becomes "************6789".

EnsureTrailingBackslash() ensures the trailing backslash. Handy when combining folder paths.

EnsureTrailingForwardslash() ensures the trailing forward slash. Handy when combining URL paths.

IfEmpty() evaluates string and if null or empty returns nullValue instead.

CompareTo() compares to the given value returning true if comparable.

TimeSpan Extensions

ToTimeString() returns a TimeSpan to HH:MM AM/PM. Examples: 1:45 PM, 12:01 AM.

Where Extensions

GetFriendlyTypeName() gets the name of the friendly type.

Where() queries a list of items that match the specified expression.

OrderBy() orders the list by the name of a property.

OrderByDescending() orders the list by the name of a property in descending order.

ThenBy() then orders the list by the name of a property.

ThenByDescending() then orders the list by a property in descending order.

Sort() sorts the object by the specified sort property.

WhereAttributeValue() filters a Query to rows that have matching attribute value.