How to get file path in C#

How could i get the right path for a file in C#?

Use openfiledialog,for following code
 
private void button1_Click(object sender,Eventargs e)
{
if(openFileDialog1.ShowDialog()==DialogResult.OK)
{
textbox1.Text=Path.GetFullPath(openFileDialog1.FileName);
}
}
 
addionally add the namespace System.IO;