Find specific pattern in a string

[ksrajalakshmi]

Hai ,

in a textbox am having text as
"(20/100)+pay1*pay2" .it's a formula. and stored in a particular
variable.
string strformula="(20/100)+pay1*pay2" ;

i've to substitute the value of the variable 'pay1' & 'pay2' and
finding the value of that strformula.
can any onr tell me how to find 'pay1' and 'pay2' in the variable
strformula. it's urgent and reply immediately.
Thanks in advance.

[Bruce Wood]

In thinking about Jon's reply using String.Replace, it occurred to me
that there's a much easier way to do this.

// Fill a Hashtable with variables and corresponding values
Hashtable variables = new Hashtable();
variables["pay1"] = 45.6;
variables["pay6"] = 100.2;
etc.

string expression = "(pay1 * pay6) * 20 / 100";

// Loop through the hashtable, replacing each variable with its value
string outExpression = expression;
foreach (DictionaryEntr y de in variables)
{
string varName = (string)de.Key;
double varValue = (double)de.Valu e;
outExpression = outExpression.R eplace(varName,
varValue.ToStri ng());
}

// outExpression will now contain "(45.6 * 100.2) * 20 / 100"

MUCH easier to read! The only downside is that it doesn't catch
invalid variable names in the expression. Of course, you could always
test outExpression against a regular expression to ensure that it
contained no variable names:

Regex identifierRegex = new Regex("[a-zA-Z][a-zA-Z0-9]*");
Match nextIdMatch = identifierRegex .Match(outExpre ssion);
if (nextIdMatch.Su ccess) { ... still a variable name in the expression
.... }