StringBuilder does not contain a definition for Append

Question

I'm having some error and I'm too much of a noob to figure out how to get around it. It's saying

Error CS1061 'StringBuilder' does not contain a definition for 'Append' and no accessible extension method 'Append' accepting a first argument of type 'StringBuilder' could be found (are you missing a using directive or an assembly reference?)

using System;

namespace Working_with_Strings  
{  
    class Program  
    {  
        static void Main(string[] args)  
        {  
  
StringBuilder myString = new StringBuilder();  
  
            for (int i = 0; i < 100; i++)  
            {  
                myString.Append("--");  
            }  

            Console.WriteLine(myString);  
            Console.ReadLine();  
       }   
 }  

}

It seems that anything I do regarding StringBuilder doesn't work. Even opening a new project and copy/pasting it directly from https://learn.microsoft.com/en-us/dotnet/standard/base-types/stringbuilder it just doesn't work.

Answer 1

No I didn't do anything outside of just try to use stringbuilder. It works normally in the video I am following, but when I do it it just throws out a bunch of errors and doesn't seem to exist for me.

When I click on it it brings me to Internal Class StringBuilder, which has nothing.

namespace Working_with_Strings
{
    internal class StringBuilder
    {
    }
}

Answer 2

Are you missing a using directive or an assembly reference?

Do you have the following at the beginning of your program (file)?

using System.Text;

If not then add that.

Answer 3

Did you define a class called StringBuilder yourself?

Hold down the Ctrl key and click on the class to see where the program will jump to?

Or hover your mouse over this class to see if it is a System.Text.StringBuilder like the picture below:

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Answer 4

What happens with using

System.Text.StringBuilder builder = new StringBuilder();
builder.Append("Hello");