string ValueInString;
foreach (char letter in ValueInString) //For each character in string 'ValueInString' perform the below
{

}

https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/foreach-in

Using foreach to loop over each character letter in a string.
Microsoft Official Reference: https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/foreach-in

Explanations from other websites:
https://www.dotnetperls.com/loop-chars
https://www.dotnetperls.com/for-foreach
https://www.dotnetperls.com/foreach

For loop using foreach on a string value

c#

C#