Few extension methods of IEnumerable in C#

Following are a few extension methods for IEnumerable<string>. Each extension method has a description, code and usage section to describe it.

public static IEnumerable<string> IfMatchWith(this IEnumerable<string> myList, string itemToMatch)

This extension method will iterate through the list and return those items matched with itemToMatch passed by the caller of this method.

public static IEnumerable<string> IfMatchWith(this IEnumerable<string> myList, string itemToMatch)
{
    foreach (var item in myList.Where(item => item == itemToMatch))
        yield return item;
}

Usage:

IList<string> myList = new List<string>() { "A", "B", "C", "D", "E" };
myList = myList.IfMatchWith("A").ToList<string>();

public static IEnumerable<string> IfNotMatchWith(this IEnumerable<string> myList, string itemToMatch)

This extension method will iterate through the list and return those not matched with itemToMatch passed by caller of this method.

public static IEnumerable<string> IfNotMatchWith(this IEnumerable<string> myList, string itemToMatch)
{
    foreach (var item in myList.Where(item => item != itemToMatch))
        yield return item;
}

Usage:

IList<string> myList = new List<string>() { "A", "B", "C", "D", "E" };
myList = myList.IfNotMatchWith("A").ToList<string>();

public static IEnumerable<string> IgnoreNullOrEmptyOrSpace(this IEnumerable<string> myList)

This extension method will iterate through the list and return those items only that matched with itemToMatch passed by caller of this method.

public static IEnumerable<string> IgnoreNullOrEmptyOrSpace(this IEnumerable<string> myList)
{
    foreach (var item in myList.Where(item => !string.IsNullOrEmpty(item) && item != " "))
        yield return item;
}

Usage:

IList<string> myList = new List<string>() { "A", "A", "A", "A", "", " ", "C", null };
myList = myList.IgnoreNullOrEmptyOrSpace().ToList<string>();

public static IEnumerable<string> MakeAllUpper(this IEnumerable<string> myList)

This extension method will iterate through the list and return those items after converting to upper case to the caller of this method.

public static IEnumerable<string> MakeAllUpper(this IEnumerable<string> myList)
{
    foreach (var item in myList)
        yield return item.ToUpper();
}

Usage:

IList<string> myList = new List<string>() { "A", "B", "c", "d", "E" };
myList = myList.MakeAllUpper().ToList<string>();

public static IEnumerable<string> MakeAllLower(this IEnumerable<string> myList)

This extension method will iterate through the list and return those items after converting to lower case to the caller of this method.

public static IEnumerable<string> MakeAllLower(this IEnumerable<string> myList)
{
    foreach (var item in myList)
        yield return item.ToLower();
}

Usage:

IList<string> myList = new List<string>() { "A", "B", "c", "d", "E" };
myList = myList.MakeAllLower().ToList<string>();

public static IEnumerable<T> MakeAllDefault<T>(this IEnumerable<T> myList)

This extension method will iterate through the list and return default values of those items to the caller of this method.

public static IEnumerable<T> MakeAllDefault<T>(this IEnumerable<T> myList)
{
    foreach (var item in myList)
        yield return default(T);
}

Usage:

IList<string> myList = new List<string>() { "A", "B", "c", "d", "E" };
myList = myList.MakeAllDefault<string>().ToList<string>();

public static IEnumerable<string> IfMatchWithPattern(this IEnumerable<string> myList, string pattern)

This extension method will iterate through the list and return those matched with the Pattern to the caller of this method.

public static IEnumerable<string> IfMatchWithPattern(this IEnumerable<string> myList, string pattern)
{
    foreach (var item in myList.Where(item => Regex.IsMatch(item, pattern)))
        yield return item;
}

Usage:

IList<string> myList = new List<string>() { "A", "B", "c", "d", "E" };
myList = myList.IfMatchWithPattern(".").ToList<string>();

public static IEnumerable<string> IfLengthEquals(this IEnumerable<string> myList, int itemLength)

This extension method will iterate through the list and return those items whose length is equal to the itemLength given by the caller of this method.

public static IEnumerable<string> IfLengthEquals(this IEnumerable<string> myList, int itemLength)
{
    foreach (var item in myList.Where(item => item.Length == itemLength))
        yield return item;
}

Usage:

IList<string> myList = new List<string>() { "A", "B", "c", "d", "E" };
myList = myList.IfLengthEquals(1).ToList<string>();

 public static IEnumerable<string> IfLengthInRange(this IEnumerable<string> myList, int startOfRange, int endOfRange)

This extension method will iterate through the list and return those items whose length is in range of startOfRange and endOfRange.

public static IEnumerable<string> IfLengthInRange(this IEnumerable<string> myList, int startOfRange, int endOfRange)
{
    foreach (var item in myList.Where(item => item.Length >= startOfRange && item.Length <= endOfRange))
        yield return item;
}

Usage:

IList<string> myList = new List<string>() { "A", "B", "c", "d", "E" };
myList = myList.IfLengthInRange(1, 2).ToList<string>();