Hi HaqBadi,
Refer the below sample.
HTML
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
<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/3.3.2/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.2/css/bootstrap.min.css" />
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-datepicker/1.5.1/css/bootstrap-datepicker.css" />
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-datepicker/1.5.1/js/bootstrap-datepicker.min.js"></script>
<script type="text/javascript">
$(function () {
$('#txtStartDate,#txtEndDate').datepicker({
format: 'dd/mm/yyyy',
autoclose: true
});
});
</script>
</head>
<body>
<form id="form1" runat="server">
<div>
<table class="table table-responsive">
<tr>
<td>
Start Date
</td>
<td>
<asp:TextBox ID="txtStartDate" CssClass="form-control" runat="server" />
</td>
</tr>
<tr>
<td>
End Date
</td>
<td>
<asp:TextBox ID="txtEndDate" runat="server" CssClass="form-control" />
</td>
</tr>
<tr>
<td>
<asp:Button Text="Display First Day" runat="server" CssClass="btn btn-primary" OnClick="Display" />
</td>
<td>
<asp:Label ID="lblFirstDay" runat="server" />
</td>
</tr>
</table>
</div>
</form>
</body>
</html>
C#
protected void Display(object sender, EventArgs e)
{
lblFirstDay.Text = "";
DateTime startDate = DateTime.ParseExact(txtStartDate.Text, "dd/MM/yyyy", System.Globalization.CultureInfo.InvariantCulture);
DateTime endDate = DateTime.ParseExact(txtEndDate.Text, "dd/M/yyyy", System.Globalization.CultureInfo.InvariantCulture);
if (startDate < endDate)
{
for (var day = startDate.Date; day.Date <= endDate.Date; day = day.AddDays(1))
{
if (day.ToString("dddd").ToUpper() == "MONDAY")
{
lblFirstDay.Text = day.ToString("dd/MM/yyyy");
break;
}
}
}
}
VB.Net
Protected Sub Display(sender As Object, e As EventArgs)
lblFirstDay.Text = ""
Dim startDate As DateTime = DateTime.ParseExact(txtStartDate.Text, "dd/MM/yyyy", System.Globalization.CultureInfo.InvariantCulture)
Dim endDate As DateTime = DateTime.ParseExact(txtEndDate.Text, "dd/M/yyyy", System.Globalization.CultureInfo.InvariantCulture)
If startDate < endDate Then
Dim day = startDate.[Date]
While day.[Date] <= endDate.[Date]
If day.ToString("dddd").ToUpper() = "MONDAY" Then
lblFirstDay.Text = day.ToString("dd/MM/yyyy")
Exit While
End If
day = day.AddDays(1)
End While
End If
End Sub
Screenshot