C#

public void DoYourThingBaby()
        {
            
            string pot = @Application.StartupPath + @"\" + lstFILES.SelectedItem;
            StreamReader sr = new StreamReader(pot);
            string tempF = sr.ReadToEnd();
            sr.Close();

            char[] tempC = tempF.ToCharArray();

            //textBox1.Text = tempF;

            int stevc=0;
            foreach(char chr in tempC)
                if(chr==Convert.ToChar(textBox1.Text))
                    stevc++;

            
        }

Matjaž Grahek wrote:

string pot = @Application.StartupPath + @"\" + lstFILES.SelectedItem;
StreamReader sr = new StreamReader(pot);
string tempF = sr.ReadToEnd();
sr.Close();

public void DoYourThingBaby()
{
    string pot = @Application.StartupPath + @"\" + lstFILES.SelectedItem;
    if(!System.IO.File.Exists(pot))
        return;
    int count = System.IO.File.ReadAllText(pot).Split('\\').Length - 1
}

int bkslashCount = 0;
string pot = Path.Combine(Application.StartupPath, lstFILES.SelectedItem); // USE Path.Combine!!
if (File.Exists(pot))
{
    string data = File.ReadAllText(pot);
    bkslashCount = data.ToCharArray().Where(c => c == '/').Count();
}