C# variable types include byte, sbyte, short, ushort, int, uint, long, ulong, float, double, decimal, char, string, enum and reference. Variable name should be consisted with letter, number and slashes only, with a letter at the beginning position.

int i=3;
int i^r=3; //error, ^ is not allowed

string ref="this is wrong"; //error, ref is a reserved keyword

using System.Windows.Forms;
class tt
{
public static string str = "test variable";
public int i = 3;
public void tweet()
{
......
}
}
MessageBox.Show(tt.str); //test variable

using System.Windows.Forms;
class tt
{
public static string str = "test variable";
public int i = 3;
public void tweet()
{
......
}
}
MessageBox.Show(tt.i); //error
tt s = new tt();
MessageBox.Show(s.i.ToString()); //3