Recipe 2.8 Comparing a String to the Beginning or End of a Second String

Problem

You need to determine whether a string is at the head or tail of a second string. In addition, the case sensitivity of the search needs to be controlled.

Solution

Use the EndsWith or StartsWith instance methods on a string object. Comparisons with EndsWith and StartsWith are always case-sensitive. The following code compares the value in the string variable head to the beginning of the string Test:

string head = "str";
string test = "strVarName";
bool isFound = test.StartsWith(head);

The following example compares the value in the string variable Tail to the end of the string test:

string tail = "Name";
string test = "strVarName";
bool isFound = test.EndsWith(tail);

In both examples, the isFound Boolean variable is set to true, since each string is found in test.

To do a case-insensitive comparison, employ the static string.Compare method. The following two examples modify the previous two examples by performing a case-insensitive comparison. The first is equivalent to a case-insensitive StartsWith string search:

string head = "str";
string test = "strVarName";
int isFound = string.Compare(head, 0, test, 0, head.Length, true);

The second is equivalent to a case-insensitive EndsWith string search:

string tail = "Name";
string test = "strVarName";
int isFound = string.Compare(tail, 0, test, (test.Length - tail.Length), 
                             tail.Length, true);

Discussion

Use the BeginsWith or EndsWith instance methods to do a case-sensitive search for a particular string at the beginning or end of a string. The equivalent case-insensitive comparison requires the use of the static Compare method in the string class. If the return value of the Compare method is zero, a match was found. Any other number means that a match was not found.

See Also

See the "String.StartsWith Method," "String.EndsWith Method," and "String.Compare Method" topics in the MSDN documentation.