Help with string manipulation function

I have a set of strings that contain within them one or more question marks delimited by a comma, a comma plus one or more spaces, or potentially both. So these strings are all possible:

BOB AND ?
BOB AND ?,?,?,?,?
BOB AND ?, ?, ? ,?
BOB AND ?,?  ,  ?,?
?,  ?               ,? AND BOB

I need to replace the question marks with @P#, so that the above samples would become:

B开发者_如何学运维OB AND @P1
BOB AND @P1,@P2,@P3,@P4,@P5
BOB AND @P1,@P2,@P3,@P4
BOB AND @P1,@P2,@P3,@P4
@P1,@P2,@P3 AND BOB

What's the best way to do this without regex or Linq?

I ignored the trimming of spaces in your output example, because if this is to be used in a SQL statement, the spaces are irrelevent. This should perform pretty well due to the use of StringBuilder rather than repeated calls to Replace, Substring, or other string methods.:

public static string GetParameterizedString(string s)
{
    var sb = new StringBuilder();
    var sArray = s.Split('?');
    for (var i = 0; i < sArray.Length - 1; i++)
    {
        sb.Append(sArray[i]);
        sb.Append("@P");
        sb.Append(i + 1);
    }
    sb.Append(sArray[sArray.Length - 1]);
    return sb.ToString();
} 

If you don't want regex or LINQ, I would just write a loop, and use the "ReplaceFirst" method from this question to loop over the string, replacing each occurrence of ? with the appropriate @P#.\

How do I replace the *first instance* of a string in .NET?

Maybe something like this:

int i = 0;
while (myString.Contains("?"))
{
    myString = myString.ReplaceFirst("?", "@P" + i);
    i++;
}

Note that "ReplaceFirst" is not a standard method on string - you have to implement it (e.g. as an extension method, in this example).

Why not generate your SQL as you get your parameters defining proper CASE in your code and give it to execution at the very end when it is ready?

If you want something out of the box :)

string toFormat = "?,  ?               ,? AND BOB";
while (toFormat.Contains("  "))
    toFormat = toFormat.Replace("  ", " ");
toFormat = toFormat.Replace("?", "{0}");
string formated = string.Format(toFormat, new PCounter());

Where PCounter is like this

class PCounter{
    int i = 0;
    public override string ToString(){
        return "@P" + (++i);
    }
}

I think something like the below should do it.

string input = "BOB AND ?,?,?,?,?";
int number = 1;
int index = input.IndexOf("?");
while (index > -1)
{
    input = input.Substring(0, index).Trim() + " @P" + number++.ToString() + input.Substring(index + 1).Trim();
    index = input.IndexOf("?");
}