c# add comma before every numbers in my string except first number

byMR

February 3, 2023

I am developing as application in asp.net mvc.

I have a string like below

string myString = "1A5#3a2@"

now I want to add a comma after every occurrence of number in my string except the first occurrence.

string myNewString "1A,5#,3a,2@";

I know I can use loop for this like below
myNewString

foreach(var ch in myString) 
{
    if (ch >= '0' && ch <= '9')     
    {                  
        myNewString = myNewString ==""?"":myNewString + "," + Convert.ToString(ch);
    }     
    else     
    {         
        myNewString = myNewString ==""? Convert.ToString(ch): myNewString + Convert.ToString(ch);     
    }
}

>Solution :

so, as I understood the below code will work for you

StringBuilder myNewStringBuilder = new StringBuilder();
foreach(var ch in myString) 
{
    if (ch >= '0' && ch <= '9')     
    {                  
        if (myNewStringBuilder.Length > 0)
        {
            myNewStringBuilder.Append(",");
        }
        myNewStringBuilder.Append(ch);
    }     
    else     
    {         
        myNewStringBuilder.Append(ch);    
    }
}
myString = myNewStringBuilder.ToString();

NOTE

Instead of using myNewString variable, I’ve used StringBuilder object to build up the new string. This is more efficient than concatenating strings, as concatenating strings creates new strings and discards the old ones. The StringBuilder object avoids this by efficiently storing the string in a mutable buffer, reducing the number of object allocations and garbage collections.