I tried to assign a value in aspx.cs file.
static String cnn;
cnn = "hi";
I get an error:
cnn is a field but used as a type
I have added the code above all functions in the class (not inside page load or any other event handler).
Why do I get this error and how can I fix it??
You can't refer to cnn outside of a function, except when declaring the field.
If you want to declare and initialize the field, this can be done in one line:
static string cnn = "hi";
Note on style - in C#, use string, not String.
cnn is referenced. Where are you trying to use it?