c# database login

Question

Hi, I made this login form and even if the username and pass are correct, my program still show "NO". Can you tell me where I do wrong?
here is the code 

 I am getting this error:   "data type mismatch in criteria expression" Can you tell me why?

here's the code 

try

{

string constring = @"Provider = Microsoft.ACE.OLEDB.12.0; Data source= bla.accdb;Persist Security Info=True;";

OleDbConnection conexiune = new OleDbConnection(constring);

OleDbCommand cmdDataBase = new OleDbCommand("Select * from Table1 where username =' " + this.textBox1.Text+"' and pass ='"+this.textBox2.Text+"';", conexiune);

OleDbDataReader myReader;

conexiune.Open();

myReader = cmdDataBase.ExecuteReader();

int count = 0;

while (myReader.Read())

{ count = count + 1; }

if (count == 1)

{

MessageBox.Show("FS");

}

else

{

MessageBox.Show("no");

}

}

catch (Exception ex)

{ MessageBox.Show(ex.Message); }

}