Q:

Incorrect Syntax near '='

i watched a course and the teacher write this code and its worked for him but shows me this error..
my CODE
private void button2_Click(object sender, EventArgs e){
 con.Open();
 SqlCommand cmd = new SqlCommand("update Admin set 
 username=@username.password=@password.Fullname=@Fullname")
 cmd.Parameters.AddWithValue("@username", textuser.Text);
 cmd.Parameters.AddWithValue("@password", textpassword.Text);
 cmd.Parameters.AddWithValue("@Fullname", textFullname.Text);
 cmd.Parameters.AddWithValue("@id", id);
 cmd.ExecuteNonQuery(); // Error In This Line...
 con.Close();
 MessageBox.Show("DELETED");
 upload_data_into_GridView_from_database();
}

A:

The dots in the query should be commas instead. And as far as your code is concerned, the query seems to be missing a where clause to filter on id (or the-like):
I would suggest:
update admin
set username = @username, password = @password, Fullname = @Fullname
where id = @id

A:

you are missing an e, in ExecuteNonQuery:
cmd.ExecuteNonQuery();

Also instead of a . you need a comma  (,) on your update query:

