I have a peculiar problem..!
I have a string with some constant value at multiple paces. For example consider the following sting.
string tmpStr = "Hello _tmp_ how is _tmp_ this possible _tmp_ in C#...?"
Now i want to replace each of the tmp in the string with values that are stored in an array, first tmp holds array[0], second tmp holds array[1] and so on...
Any idea how this can be achieved..? I use C# 2.0
How about this:
string input = "Hello _tmp_ how is _tmp_ this possible _tmp_ in C#...?";
string[] array = { "value1", "value2", "value3" };
Regex rx = new Regex(@"\b_tmp_\b");
if (rx.Matches(input).Count <= array.Length)
{
int index = 0;
string result = rx.Replace(input, m => array[index++]);
Console.WriteLine(result);
}
You need to ensure the number of matches found is never greater than the array's length, as demonstrated above.
EDIT: in response to the comment, this can easily work with C# 2.0 by replacing the lambda with this:
string result = rx.Replace(input, delegate(Match m) { return array[index++]; });
MatchEvaluator. Each match found is replaced by an element of the array. So the 1st match is replaced with array[0] then index++ will set index to 1, then the next match will be advanced to the value of array[1] and so forth.index variable so that it can be advanced correctly for each match. Had I used array[index++] alone then it would've evaluated once and used value1 repeatedly, contrary to the goal of the question. You may want to refer to Jon Skeet's article on closures for more details: csharpindepth.com/Articles/Chapter5/Closures.aspx
MatchEvaluator you provided will be strict left to right? In other words, what if the delegate method will invoke for second match and then for first match for example. In this hypothetical case replacement will be performed incorrectly. I understand that left to right flow is common for regex implementation, but however, what if? If you have any links that can dispel my doubts, could you provide them.you can use a MatchEvaluator (a function that gets called to do do each replacement), some examples here:
http://msdn.microsoft.com/en-us/library/aa332127%28VS.71%29.aspx
suggestion, you can use string.Split() to split on "tmp". then iterate the list of splitted items and print them + the array values out eg pseudocode idea only
string[] myarray = new string[] { 'val1', 'val2' };
string s = "Hello _tmp_ how is _tmp_ this possible _tmp_ in C#";
string[] items = s.Split("tmp");
for (int i = 0; i < items.Length; i++)
{
Console.WriteLine(parts[i] + myarray[i] ) ;
}
I would think that Ahmad Mageed's first solution is the one to go for because array[index++] is only evaluated once when passed into the rx.Replace method..
I compiled it too to verify whether I understand it correctly or not, and sure enough it produces the following output:
Hello value1 how is value1 this possible value1 in C#...?
Has the behaviour changed with the later versions of the framework? or am I mistaken in thinking that the expected output should be:
Hello value1 how is value2 this possible value3 in C#...?
array[index++] directly as I did before I rolled my answer back. That does give value1 over and over. The reason the 2nd approach worked is because the index variable is captured by the delegate. See Jon Skeet's article on Closures for more info: csharpindepth.com/Articles/Chapter5/Closures.aspx