OpenFileDialog :
private void openFIleToolStripMenuItem_Click(object sender, EventArgs e){
string ChosenFile = "";
openFileDialog1.FileName = "";
openFileDialog1.Filter = "png(*.png)|*.png|ALL Files(*.*)|*.*";
ChosenFile = openFileDialog1.FileName;
if (openFileDialog1.ShowDialog() == System.Windows.Forms.DialogResult.OK)
{
}
}
SaveASFileDialog:
your code.ShowSaveAsDialog();