Problems i have regarding database connection with login

[Coldflame]

Hello,

this is my first time posting. and just so you know i'm an ASP.NET noob
this year i got a project in school and it suposed to be made in asp.net thus thats why i'm learing. i'll provide you with as much info as i can

anyway, the "idea" is to make an evaluation site that has a members that can login, and an admin + sub admin. all of this has to be connected with a database ( ofc ).

now the place where i am stuck, or that i experiance problems is this:
i have my database and my database connection. i can already write in the database because i made the "register users".
However. i just cant seem to fix my Login
i dont know how to get the values that you write into the texboxes on the site and then "accept" these and and get those out of the database.
eg: i type Test1 (as username) and qwerty1 (as password).
lets say this exists in my database. how can i check that and actuallly log in ?

i have my Login.aspx that has this:

<asp:Login ID="LoginUser" runat="server" EnableViewState="false" RenderOuterTable="false">
        <LayoutTemplate>
            <span class="failureNotification">
                <asp:Literal ID="FailureText" runat="server"></asp:Literal>
            </span>
            <asp:ValidationSummary ID="LoginUserValidationSummary" runat="server" CssClass="failureNotification" 
                 ValidationGroup="LoginUserValidationGroup"/>
            <div class="accountInfo">
                <fieldset class="login">
                    <legend>Account Informatie</legend>
                    <p>
                        <asp:Label ID="UserNameLabel" runat="server" AssociatedControlID="UserName">Gebruikersnaam:</asp:Label>
                        <asp:TextBox ID="UserName" runat="server" CssClass="textEntry"></asp:TextBox>
                        <asp:RequiredFieldValidator ID="UserNameRequired" runat="server" ControlToValidate="UserName" 
                             CssClass="failureNotification" ErrorMessage="Gebruikersnaam is vereist." ToolTip="Gebruikersnaam is vereist." 
                             ValidationGroup="LoginUserValidationGroup">*</asp:RequiredFieldValidator>
                    </p>
                    <p>
                        <asp:Label ID="PasswordLabel" runat="server" AssociatedControlID="Password">Passwoord:</asp:Label>
                        <asp:TextBox ID="Password" runat="server" CssClass="passwordEntry" TextMode="Password"></asp:TextBox>
                        <asp:RequiredFieldValidator ID="PasswordRequired" runat="server" ControlToValidate="Password" 
                             CssClass="failureNotification" ErrorMessage="Passwoord is vereist." ToolTip="Passwoord is vereist." 
                             ValidationGroup="LoginUserValidationGroup">*</asp:RequiredFieldValidator>
                    </p>
                    <p>
                        <asp:CheckBox ID="RememberMe" runat="server" Visible="false" />
                        <asp:Label ID="RememberMeLabel" runat="server" AssociatedControlID="RememberMe" CssClass="inline" Visible="false">Keep me logged in</asp:Label>
                    </p>
                </fieldset>
                <p class="submitButton">
                    <asp:Button ID="LoginButton" runat="server" CommandName="Login" Text="Log In" ValidationGroup="LoginUserValidationGroup" onclick="btnAanmelden_Click"/>
                </p>
            </div>
        </LayoutTemplate>
    </asp:Login>

+ the C# file

  public partial class Login : System.Web.UI.Page
    {
        SqlConnection con;
        SqlCommand cmd;

        protected void Page_Load(object sender, EventArgs e)
        {
            RegisterHyperLink.NavigateUrl = "Register.aspx?ReturnUrl=" + HttpUtility.UrlEncode(Request.QueryString["ReturnUrl"]);

            string connstring = ConfigurationManager.ConnectionStrings["ConnectionTest"].ConnectionString;
con = new SqlConnection(connstring);
        }
        protected void btnAanmelden_Click(object sender, EventArgs e)
        {

try {
con.Open();
cmd = new SqlCommand("Select (pasworod,gebruikers_naam) from Gebruiker where gebruiker_naam= values('"+ Username + "'", con);
}
catch (Exception)
{throw;}


        }
public bool UserName{get;set;}
    }

any help would be very appreciated i've been stuck at this for serveral days now.