C# String Methods IsEmpty, Find, Replace

IsEmpty, Find, and Replace are common used string methods in MFC (CString class).

MFC (CString) Samples:
CString somestring = L"ABCDEFG";

if (somestring.IsEmpty())
{
    // somestring is empty
}

if (somestring.Find(L"ABC")!=-1)
{
    // found "ABC" in somestring
}

somestring.Replace(L"ABC",L"abc");
// somestring == L"abcDEFG"

In C# we use string.IsNullOrEmpty instead of IsEmpty and IndexOf instead of Find:

See also: Comparison of string operations: Left, Mid, Right - C# vs MFC

Check for an Empty String: IsNullOrEmpty in C#

Checks if a string is Null or Empty:

// Sample: Check if somestring is empty
string somestring = string.Empty;
if (string.IsNullOrEmpty(somestring))
{
    // somestring is empty
}

Don't use comparisons like:
if (somestring.Length==0) ... or
if (somestring=="") ...
The comparison will result in an exception(!) if somestring == string.Empty or somestring == Null (no object available)

Search in a String: IndexOf in C#

Search for a string inside a string and return the index ( index==-1 if string not found)

// Sample: Search for "DEF" inside "ABCDEFG"
string somestring = "ABCDEFG";
int index = somestring.IndexOf("DEF");
// index == 3 (starts by 0)

if (index == -1)
{
    // not found
}

Replace String in C#

Replace a string inside a string:

// Sample: Replace "ABC" with "abc" inside "ABCDEFG"
string somestring = "ABCDEFG";
somestring = somestring.Replace("ABC","abc");
// somestring == "abcDEFG"

"Replace" returns a new string ... it does not change the "old" string, so you need to use: "somestring = somestring.Replace(...)"