change password in asp.net using Entity Framework

Question

i want when user wants to change password its first enter existing password then new password...

<table class="style1">
<tr>
<td>Current Password:</td>
<td>
<asp:TextBox ID="TxtCrntPswd" runat="server"></asp:TextBox>
</td>
</tr>
<tr>
<td>New Password:</td>
<td>
<asp:TextBox ID="TxtNwPswd" runat="server"></asp:TextBox>
</td>
</tr>
<tr>
<td>Confirm New Password:</td>
<td>
<asp:TextBox ID="TxtCnPswd" runat="server"></asp:TextBox>
</td>
<td>
<asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server"
ControlToValidate="TxtCnPswd" ErrorMessage="!!" ForeColor="Red"
SetFocusOnError="True"></asp:RequiredFieldValidator>
<asp:CompareValidator ID="CompareValidator1" runat="server"
ControlToCompare="TxtNwPswd" ControlToValidate="TxtCnPswd"
ErrorMessage="The new password and confirm password not same !!" ForeColor="Red"></asp:CompareValidator>
</td>
</tr>
</table>
</div>
<asp:Button ID="BtnPswd" runat="server" Text="Save" OnClick="BtnPswd_Click" />

protected void BtnPswd_Click(object sender, EventArgs e)
{
using (var context = new schoolEntities6())
{
string strmsg = string.Empty;
byte[] encode = new byte[TxtCnPswd.Text.ToString().Length];
encode = Encoding.UTF8.GetBytes(TxtCnPswd.Text);
strmsg = Convert.ToBase64String(encode);
encrypwd = strmsg;
var currPass = TxtCrntPswd.Text;
var newPass = TxtNwPswd.Text;
var rePass = strmsg;
User userEntity = (from x in context.Users
where
x.Password == TxtCrntPswd.Text
select x).FirstOrDefault();
//if (userEntity != null)
{
userEntity.Password = TxtCnPswd.Text;
context.SaveChanges();
}
else
{
lbl_msg.Text = "current password is incorrect";
}
}

This scenario isn't working