Prevent insert record between two Dates if Exists in ASP.Net

Hi,

Please refer below sample.

HTML

<div>
    From :
    <asp:TextBox ID="txtFromDate" runat="server"></asp:TextBox>
    <br />
    To :
    <asp:TextBox ID="txtToDate" runat="server"></asp:TextBox>
    <asp:Button ID="btnInsert" Text="Insert" runat="server" OnClick="btnInsert_Click" />
    <asp:Label ID="lblMessage" runat="server" />
</div>

Namespaces

C#

using System.Globalization;
using System.Data;

VB.Net

Imports System.Globalization
Imports System.Data

Code

C#

protected void btnInsert_Click(object sender, EventArgs e)
{
    DataTable dt = new DataTable();
    dt.Columns.AddRange(new DataColumn[] { new DataColumn("FromDate", typeof(string)), new DataColumn("ToDate", typeof(string)) });
    dt.Rows.Add("01.08.2018", "15.08.2018");
    DateTime fromdate = DateTime.ParseExact(txtFromDate.Text, "dd.MM.yyyy", CultureInfo.CurrentUICulture);
    DateTime ToDate = DateTime.ParseExact(txtToDate.Text, "dd.MM.yyyy", CultureInfo.CurrentUICulture);
    int fromDay = fromdate.Day;
    int fromMonth = fromdate.Month;
    int FromYear = fromdate.Year;

    string dtFromDay = dt.Rows[0]["FromDate"].ToString();
    string[] dtFromsplit = dtFromDay.Split('.');
    string dtToDay = dt.Rows[0]["ToDate"].ToString();
    string[] dtTosplit = dtToDay.Split('.');

    int toDay = ToDate.Day;
    int toMonth = ToDate.Month;
    int toYear = ToDate.Year;
    if (fromDay >= Convert.ToInt16(dtFromsplit[0]) && fromMonth >= Convert.ToInt16(dtFromsplit[1]) && FromYear >= Convert.ToInt16(dtFromsplit[2]) && toDay >= Convert.ToInt16(dtTosplit[0]) && toMonth >= Convert.ToInt16(dtTosplit[1]) && FromYear >= Convert.ToInt16(dtTosplit[2]))
    {
        ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('Valid Input')", true);
    }

    else
    {
        ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('Invalid Input')", true);
    }
}

VB.Net

Protected Sub btnInsert_Click(ByVal sender As Object, ByVal e As EventArgs)
    Dim dt As DataTable = New DataTable()
    dt.Columns.AddRange(New DataColumn() {New DataColumn("FromDate", GetType(String)), New DataColumn("ToDate", GetType(String))})
    dt.Rows.Add("01.08.2018", "15.08.2018")
    Dim fromdate As DateTime = DateTime.ParseExact(txtFromDate.Text, "dd.MM.yyyy", CultureInfo.CurrentUICulture)
    Dim ToDate As DateTime = DateTime.ParseExact(txtToDate.Text, "dd.MM.yyyy", CultureInfo.CurrentUICulture)
    Dim fromDay As Integer = fromdate.Day
    Dim fromMonth As Integer = fromdate.Month
    Dim FromYear As Integer = fromdate.Year
    Dim dtFromDay As String = dt.Rows(0)("FromDate").ToString()
    Dim dtFromsplit As String() = dtFromDay.Split("."c)
    Dim dtToDay As String = dt.Rows(0)("ToDate").ToString()
    Dim dtTosplit As String() = dtToDay.Split("."c)
    Dim toDay As Integer = ToDate.Day
    Dim toMonth As Integer = ToDate.Month
    Dim toYear As Integer = ToDate.Year
    If fromDay >= Convert.ToInt16(dtFromsplit(0)) AndAlso fromMonth >= Convert.ToInt16(dtFromsplit(1)) AndAlso FromYear >= Convert.ToInt16(dtFromsplit(2)) AndAlso toDay >= Convert.ToInt16(dtTosplit(0)) AndAlso toMonth >= Convert.ToInt16(dtTosplit(1)) AndAlso FromYear >= Convert.ToInt16(dtTosplit(2)) Then
        ScriptManager.RegisterClientScriptBlock(Me, Me.[GetType](), "alertMessage", "alert('Valid Input')", True)
    Else
        ScriptManager.RegisterClientScriptBlock(Me, Me.[GetType](), "alertMessage", "alert('Invalid Input')", True)
    End If
End Sub

Screenshot