Actually what you pass as the first parameter in builder of FileStream
is not the name of the file, but the address (path) of the archive.
Its address must contain the path, name and extension of the file in one string.
So after getting the file name you should concatenate the rest of the information to get the full address:
string strNomeArquivo = Convert.ToString(DateTime.Now.ToFileTime()),
localizacaoArquivo = "c:/",
extensaoArquivo = ".png",
enderecoArquivo = localizacaoArquivo + strNomeArquivo + extensaoArquivo;
FileStream fs = new FileStream(enderecoArquivo, FileMode.CreateNew, FileAccess.Write);
...
Note that if you want the path of some default Windows folder, you can get them using the Enum of special system folders.
To the folder My Images user, for example:
string localizacaoArquivo = Environment.GetFolderPath(Environment.SpecialFolder.MyPictures);
my system created the file in the default directory with name ex: Cache131113874626944091 and did not execute the expected action
– Marlon Pereira
string strNomeArquivo = Convert.ToString("Cache\\" + txtUsuario.Text + DateTime.Now.ToFileTime() + ".ebtemp"),
 extensaoArquivo = "",
 enderecoArquivo = strNomeArquivo + extensaoArquivo;
 FileStream fs = new FileStream(enderecoArquivo, FileMode.Create, FileAccess.ReadWrite);
 fs.Write(vetorImagem, 0, vetorImagem.Length);
 fs.Flush();
 fs.Close();
 pbDefault.Visible = false;
 pbUsuario.Image = Image.FromFile(strNomeArquivo);
Modified and worked!– Marlon Pereira