Clear ASP.Net TextBox value and CheckBoxList selection on jQuery Sweet alert Ok Button Click using C# and VB.Net

Hidemocloud,

You need to use .then and do the TextBox and CheckBox clear using jQuery. Create a JavaScript function and call it in code behind. 

Refer below example.

HTML

<asp:TextBox ID="TextBox4" runat="server" Text="Test 1"></asp:TextBox><br />
<asp:TextBox ID="TextBox5" runat="server" Text="Test 2"></asp:TextBox><br />
<asp:TextBox ID="TextBox6" runat="server" Text="Test 3"></asp:TextBox><br />
<asp:CheckBoxList ID="CheckBoxList1" name="Test" runat="server" OnSelectedIndexChanged="CheckBox1_CheckedChanged"
    AutoPostBack="true">
    <asp:ListItem Value="Monday">Monday</asp:ListItem>
</asp:CheckBoxList>
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/bluebird/3.3.5/bluebird.min.js"></script>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<script type="text/javascript" src="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" />
<script type="text/javascript" src='https://cdn.jsdelivr.net/sweetalert2/6.3.8/sweetalert2.min.js'> </script>
<link rel="stylesheet" media="screen" href='https://cdn.jsdelivr.net/sweetalert2/6.3.8/sweetalert2.min.css' />
<link rel="stylesheet" media="screen" href='https://cdn.jsdelivr.net/sweetalert2/6.3.8/sweetalert2.css' />
<script type="text/javascript">
    function AlertClear(selected) {
        swal({ text: "Not available" }).then(function () {
            document.getElementById('<%=TextBox4.ClientID%>').value = "";
            document.getElementById('<%=TextBox5.ClientID%>').value = "";
            var checkboxes = $('#CheckBoxList1').find('input[type="checkbox"]');
            for (var i = 0; i < checkboxes.length; i++) {
                if (checkboxes[i].value == selected) {
                    checkboxes[i].checked = false;
                }
            }
        });
    }
</script>

C#

protected void CheckBox1_CheckedChanged(object sender, EventArgs e)
{
    ScriptManager.RegisterStartupScript(this, this.GetType(), "key", "window.onload = function() { AlertClear('" + CheckBoxList1.SelectedValue + "'); };", true);
}

VB.Net

Protected Sub CheckBox1_CheckedChanged(ByVal sender As Object, ByVal e As EventArgs)
    ScriptManager.RegisterStartupScript(Me, Me.[GetType](), "key", "window.onload = function() { AlertClear('" & CheckBoxList1.SelectedValue & "'); };", True)
End Sub

Screenshot