No mapping exists from object type System.Windows.Forms.RichTextBox to a known managed provider native type.'

Question

I have used rich text box to collect remarks but its not being saved in the database

here is the code

            con.Open();
            SqlCommand cmd = new SqlCommand(@"insert into Student_Records(FirstName,LastName,ContactNumber,DOB,TemporaryAddress,PermanentAddress,FatherName,Fathersoccupation,ContactNumberF,MotherName,Mothersoccupation,ContactNumberM,Remarks) values(@firstname,@lastname,@contactnumber,@dob,@temporaryaddress,@permanentaddress,@fathername,@fatheroccupation,@contactnumberf,@mothername,@motheroccupation,@contactnumberm,@remarks)", con);
            cmd.Parameters.AddWithValue("@firstname", txtFname.Text);
            cmd.Parameters.AddWithValue("@lastname", txtlastN.Text);
            cmd.Parameters.AddWithValue("@contactnumber", txtCN.Text);
            cmd.Parameters.AddWithValue("@dob", dtdob.Value);
            cmd.Parameters.AddWithValue("@temporaryaddress", txtTaddress.Text);
            cmd.Parameters.AddWithValue("@permanentaddress", txtPaddress.Text);
            cmd.Parameters.AddWithValue("@fathername", txtFname.Text);
            cmd.Parameters.AddWithValue("@fatheroccupation", txtFoccupation.Text);
            cmd.Parameters.AddWithValue("@contactnumberf", txtFcn.Text);
            cmd.Parameters.AddWithValue("@mothername", txtMname.Text);
            cmd.Parameters.AddWithValue("@motheroccoupation", txtMoccupation.Text);
            cmd.Parameters.AddWithValue("@contactnumberm", txtMcn);
            cmd.Parameters.AddWithValue("@remarks", rtremarks.Rtf);
            cmd.ExecuteNonQuery();
            con.Close();

Answer 1

In this line

cmd.Parameters.AddWithValue("@contactnumberm", txtMcn);

you're passing the TextBox itself, not its Text property.

Having said that, that will give a slightly different error. As noted in your other question about this piece of code, please post code and errors verbatim at the time you get the error, otherwise you may not get helpful answers. (Either that or you have named txtMcn inconsistently!)