How can i get current logged in user and Role?

Question

I have a login form and MDI form in C# winform application i want to hide some objects from MDI form based on their role or permission but how can i get the logged in user?

here is login.cs

 private void btnLogin_Click(object sender, EventArgs e)
        {
            if (txt_UserName.Text == "" || txt_Password.Text == "")
            {
                MessageBox.Show("Please Provide User Name and Password");
                return;
            }
            try
            {
                //Create SqlConnection
                SqlConnection con = new SqlConnection(cs);
                SqlCommand cmd = new SqlCommand("Select * from Users where UserName=@username and Password=@password", con);
                cmd.Parameters.AddWithValue("@username", txt_UserName.Text);
                cmd.Parameters.AddWithValue("@password", txt_Password.Text);
                con.Open();
                SqlDataAdapter adapt = new SqlDataAdapter(cmd);
                DataSet ds = new DataSet();
                adapt.Fill(ds);
                con.Close();
                int count = ds.Tables[0].Rows.Count;
                //If count is equal to 1, than show frmMain form
                if (count == 1)
                {

                    this.Hide();
                    frmMain frm = new frmMain();
                    frm.Show();
                }
                else
                {
                    MessageBox.Show("Login Failed!");
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }


}

// Roles table

CREATE TABLE [dbo].[Roles](
    [Roleid] [int] NOT NULL,
    [RoleName] [varchar](50) NULL,
 CONSTRAINT [PK_Roles] PRIMARY KEY CLUSTERED 
(
    [Roleid] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

SET ANSI_PADDING OFF
GO

//Users Table

CREATE TABLE [dbo].[Users](
    [UserId] [int] IDENTITY(1,1) NOT NULL,
    [RoleId] [int] NULL,
    [UserName] [varchar](25) NULL,
    [Password] [varchar](50) NULL,
 CONSTRAINT [PK_Users] PRIMARY KEY CLUSTERED 
(
    [UserId] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY],
 CONSTRAINT [IX_Users] UNIQUE NONCLUSTERED 
(
    [UserName] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

SET ANSI_PADDING OFF
GO

ALTER TABLE [dbo].[Users]  WITH CHECK ADD  CONSTRAINT [FK_Users_Roles] FOREIGN KEY([RoleId])
REFERENCES [dbo].[Roles] ([Roleid])
GO

ALTER TABLE [dbo].[Users] CHECK CONSTRAINT [FK_Users_Roles]
GO