How to add database validation for c# windows form

try

{

byte[] img = null;

FileStream fs = new FileStream(imgLoc, FileMode.Open, FileAccess.Read);

BinaryReader br = new BinaryReader(fs);

img = br.ReadBytes((int)fs.Length);

//cmd.CommandText = "INSERT INTO UserInfo (User_Name,Email,EPF_Number,Department,Laptop_Model,Laptop_Serial,Issu_Date,Hostname,)VALUES (@Name,@Email,@EPFNumber,@DPT,@Model,@Serial,@Date,@Host)";

//string sql = "INSERT INTO UserInfo (User_Name,Email,EPF_Number,Department,Laptop_Model,Laptop_Serial,Issu_Date,Hostname,Image) VALUES ( @Name,@Email,@EPFNumber,@DPT,@Model,@Serial,@Date,@Host,@Photo)";

string sql = "INSERT INTO UserInfo (User_Name,Email,EPF_Number,Department,Laptop_Model,Laptop_Serial,Issu_Date,Hostname,Image) VALUES ( @Name,@Email,@EPFNumber,@DPT,@Model,@Serial,@Date,@Host,@Photo)";

if (conn.State != ConnectionState.Open)

conn.Open();

cmd = new SqlCommand(sql, conn);

cmd.Parameters.Add(new SqlParameter("@Photo", img));

cmd.Parameters.AddWithValue("@Name", txtUserName.Text);

cmd.Parameters.AddWithValue("@Email", txtEmail.Text);

cmd.Parameters.AddWithValue("@EPFNumber", txtEPF.Text);

cmd.Parameters.AddWithValue("@DPT", cmbDpt.Text);

cmd.Parameters.AddWithValue("@Model", cmbLmdl.Text);

cmd.Parameters.AddWithValue("@Serial", cmdSerl.Text);

cmd.Parameters.AddWithValue("@Date", dobPicker.Text);

cmd.Parameters.AddWithValue("@Host", cmbHostName.Text);

conn.Close();

cmd.Connection = conn;

conn.Open();

int i = cmd.ExecuteNonQuery();

if (i > 0)

{

MessageBox.Show("Successflully Saved");

}

else

{

MessageBox.Show("Error occured");

}

conn.Close();

cmd.Parameters.Clear();

}

catch (Exception ex)

{

MessageBox.Show(ex.Message);

}

finally

{

conn.Close();

}

}

}

}