Hi fahimahmed,
In order to set the date the date should take the format YYYY-MM-DD.
Single digit days and months should be padded with a 0.
Check the example.
HTML
<asp:TextBox ID="PurchaseDate" runat="server" type="date" CssClass="form-control" />
C#
protected void Page_Load(object sender, EventArgs e)
{
PurchaseDate.Text = "2019-11-30";
}
VB.Net
Protected Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs) Handles Me.Load
PurchaseDate.Text = "2019-11-30"
End Sub
Screenshot