Okay so this source has a few errors in it but it should give you a basic idea. Then you can either figure out how to use Convert.ToDateTime(bool Value); or you can use substrings to retrieve and convert the values. The snippet of substrings for this that I typed up is a little long and can be shortened greatly, so jusst go through and see if you can figure it out from there. I don't give people exact code they are looking for, but this code is close to what you want and the time isn't any more difficult than this.
int Month = 0;
int Day = 0;
int Year = 0;
string x = "";
x += textBox1.Text.Substring(0, 1);
x += textBox1.Text.Substring(1, 1);
Month = Convert.ToInt32(x);
x = "";
x += textBox1.Text.Substring(3, 1);
x += textBox1.Text.Substring(4, 1);
Day = Convert.ToInt32(x);
x = "";
x += textBox1.Text.Substring(6, 1);
x += textBox1.Text.Substring(7, 1);
Year = Convert.ToInt32(x);
DateTime dt = new DateTime();
dt.Month = Month;
dt.Day = Day;
dt.Year = 1900 + Year;