Which substring of the string1 matches with the string2

There are two strings.

String str1="Order Number Order Time Trade Number";

String str2="Order Tm"; Then I want to know that str2 matches with which substring in the str1.

string regex = Regex.Escape(str2.Replace(@"\ ", @"\s*");
bool isColumnNameMatched = Regex.IsMatch(str1, regex, RegexOptions开发者_StackOverflow.IgnoreCase);

I am using regex because "Order Tm" will also matches "Order Time".It gives bool value that matches occurred or not.

Like str2="Order Tm" then it should return like in the str1,Order Time is the substring where matches is occurred.

Your question is very unclear and your code does not compile.
There are some problems:

1. You replace "\ " with @"\s*" - but you should replace just " " without \
2. You can't use Regex.Escape() this way. It will double your \ and result in another regex which is not working. For instance your \s* will become \\s*
3. It seems that you want to match only one word (that's where your question is unclear). In this case you should match against something like "Order|Tm"
4. To get the matched word you need a grouping construct:

Example:

var str1 = "Order Number Order Time Trade Number";
var str2 = "(Order|Tm)";
string regex = str2.Replace( @" ", @"\s*" );
var match = Regex.Match( str1, regex );

match.Success; // results in "true"
match.Value; // results in "Order"