Login and Logout Using C#.net and SQL Server 2005

/****** Object:  Table [dbo].[tbluser]    Script Date: 07/11/2016 11:58:48 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE TABLE [dbo].[tbluser](
	[ID] [INT] IDENTITY(1,1) NOT NULL,
	[Name] [nvarchar](50) NULL,
	[UNAME] [nvarchar](50) NULL,
	[PASS] [nvarchar](MAX) NULL,
	[UTYPE] [NCHAR](20) NULL,
 CONSTRAINT [PK_tbluser] PRIMARY KEY CLUSTERED 
(
	[ID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

INSERT INTO [dbo].[tbluser]
           (Name
           ,UNAME
           ,PASS
           ,UTYPE)
VALUES ('Janno Palacios',janobe,janobe,'Administrator')

   //initialize all classes
        SqlConnection conn = new SqlConnection();
        SqlCommand cmd = new SqlCommand();
        SqlDataAdapter da = new SqlDataAdapter();
        DataTable dt = new DataTable();
 
        //declaring variables
        string strquery;
        int  max;

//set a connection between SQL server and Visual C#
conn.ConnectionString = "Data Source=.\\SQLEXPRESS;database=userdb;trusted_connection=true;";

           try
           {
                conn.Open();
                //create a query for retrieving data in the database.
                strquery = "SELECT * FROM tbluser WHERE UNAME='" + txtUsername.Text + "' and PASS='" + txtPassword.Text + "'";
                //initialize new Sql commands
                cmd = new SqlCommand();
                //hold the data to be executed.
                cmd.Connection = conn;
                cmd.CommandText = strquery;
                //initialize new Sql data adapter
                da = new SqlDataAdapter();
                //fetching query in the database.
                da.SelectCommand = cmd;
                //initialize new datatable
                dt = new DataTable();
                //refreshes the rows in specified range in the datasource. 
                da.Fill(dt);
                //getting the total row in the table.
                max= dt.Rows.Count;
                //validating the total rows in the table
                if (max > 0)
                {
                    //popup message
                    MessageBox.Show("Welcome " + dt.Rows[0].Field<string>("UTYPE"));
                    //disable the group box.
                    groupBox1.Enabled = false;
                    //store the value in the Button
                    btnLogin.Text = "Logout";
 
                    //clearing textboxes
                    txtPassword.Clear();
                    txtUsername.Clear();
                }
                else
                {
                    //when the account does not exist, it will display this message.
                    MessageBox.Show("Account does not exist.");
                }
 
 
            }
            catch (Exception ex)
            {
                //catching error
                MessageBox.Show(ex.Message);
            }
            finally
            {
                da.Dispose();
                conn.Close();
            }

           if (btnLogin.Text == "Logout")
            {
                groupBox1.Enabled = true;
                txtUsername.Clear();
                txtPassword.Clear();
                btnLogin.Text = "Login";
            }
            else
            {
                groupBox1.Enabled = true  ;
                txtUsername.Clear();
                txtPassword.Clear();
                btnLogin .Text = "Login";
            }