Strange that this famous and old question has not an answer that suggests the builtin DataTable.Compute
-“trick”. Here it is.
double result = Convert.ToDouble(new DataTable().Compute("1 + 2 * 7", null));
The following arithmetic operators are supported in expressions:
+ (addition)
- (subtraction)
* (multiplication)
/ (division)
% (modulus)
More informations: DataColumn.Expression
at Expression Syntax.