Check for Valid Date using JavaScript

The following code is helpful to Validate a Date using javascript.

1. Call the Function "OnClientClick" of Button (OnClientClick="ValidateForm())
2. Write the Following Functions in Script tag of Head Section.

Javascript :

    // Declaring valid date character, minimum year and maximum year
    var dtCh= "/";
    var minYear=1900;
    var maxYear=2100;
    
    function isInteger(s)
    {
        var i;
        for (i = 0; i <>
        {
            // Check that current character is number.
            var c = s.charAt(i);
            if (((c < "0") || (c > "9"))) return false;
        }
        // All characters are numbers.
        return true;
    }

    function stripCharsInBag(s, bag)
    {
        var i;
        var returnString = "";
        // Search through string's characters one by one.
        // If character is not in bag, append to returnString.
        for (i = 0; i <>
        {
            var c = s.charAt(i);
            if (bag.indexOf(c) == -1) returnString += c;
        }
        return returnString;
    }

    function daysInFebruary (year)
    {
        // February has 29 days in any year evenly divisible by four,
        // EXCEPT for centurial years which are not also divisible by 400.
        return (((year % 4 == 0) && ( (!(year % 100 == 0)) || (year % 400 == 0))) ? 29 : 28 );
    }
    
    function DaysArray(n)
    {
        for (var i = 1; i <= n; i++)
        {
            this[i] = 31
            if (i==4 || i==6 || i==9 || i==11) {this[i] = 30}
            if (i==2) {this[i] = 29}
        }
        return this
    }

    function isDate(dtStr)
    {
        var daysInMonth = DaysArray(12)
        var pos1=dtStr.indexOf(dtCh)
        var pos2=dtStr.indexOf(dtCh,pos1+1)
        var strMonth=dtStr.substring(0,pos1)
        var strDay=dtStr.substring(pos1+1,pos2)
        var strYear=dtStr.substring(pos2+1)
        strYr=strYear
        if (strDay.charAt(0)=="0" && strDay.length>1)
        strDay=strDay.substring(1)
        if (strMonth.charAt(0)=="0" && strMonth.length>1)
        strMonth=strMonth.substring(1)
        
        for (var i = 1; i <= 3; i++)
        {
            if (strYr.charAt(0)=="0" && strYr.length>1)
            strYr=strYr.substring(1)
        }
        
        month=parseInt(strMonth)
        day=parseInt(strDay)
        year=parseInt(strYr)
        
        if (pos1==-1 || pos2==-1)
        {
            alert("The date format should be : mm/dd/yyyy")
            return false
        }
        if (strMonth.length<1>12)
        {
            alert("Please enter a valid month")
            return false
        }
        if (strDay.length<1>31 || (month==2 && day>daysInFebruary(year)) || day > daysInMonth[month])
        {
            alert("Please enter a valid day")
            return false
        }
        if (strYear.length != 4 || year==0 || yearmaxYear)
        {
            alert("Please enter a valid 4 digit year between "+minYear+" and "+maxYear)
            return false
        }
        if (dtStr.indexOf(dtCh,pos2+1)!=-1 || isInteger(stripCharsInBag(dtStr, dtCh))==false)
        {
            alert("Please enter a valid date")
            return false
        }
        return true
    }

    function ValidateForm()
    {
        var dt;
        dt=document.getElementById('txtDate');
        if (isDate(dt.value)==false)
        {
            dt.focus()
            return false
        }
        return true
    }

Reflection

Reflection is one of the features of .Net framework and has greater importance during the development of large applications.

In brief it is a powerful way of collecting and manipulate information present in application's assemblies and its metadata. Metadata contain all the Type information used by the application. The ability to obtain information at run time also makes it even more advantageous.

When reflection is used along with system.type, it allows the developer to get the valuable information about all the types and about the assemblies. We can even create the instances and then invoke various types that are used across the application.

What is Reflection?

• Reflection is the ability to find out information about objects, the application details (assemblies), its metadata at run-time.
• This allows application to collect information about itself and also manipulate on itself.
• It can be used effectively to find all the types in an assembly and/or dynamically invoke methods in an assembly.
• This includes information about the type, properties, methods and events of an object and to invoke the methods of object Invoke method can be used too.
• With reflection we can dynamically create an instance of a type, bind the type to an existing object, or get the type from an existing object and invoke its methods or access its fields and properties.
• If Attributes (C#) are used in application, then with help of reflection we can access these attributes.
• It can be even used to emit Intermediate Language code dynamically so that the generated code can be executed directly.

How to use Reflection in our applications?

• System.Reflection namespace contains all the Reflection related classes. These classes are used to get information from any of the class under .NET framework.
• The Type class is the root of all reflection operations. Type is an abstract base class that acts as means to access metadata though the reflection classes.
• Using Type object, any information related to methods, implementation details and manipulating information can be obtained.
• The types include the constructors, methods, fields, properties, and events of a class, along with this the module and the assembly in which these information are present can be accessed and manipulated easily.
• we can use reflection to dynamically create an instance of any type, bind the type to an existing object, or get the type from an existing object.
• Once this is done appropriate method can be invoked, access the fields and properties.
• This can be done by specifying the Type of object or by specifying both assembly and Type of the object that needs to be created.
• By this the new object created acts like any other object and associated methods, fields and properties can be easily accessed.
• With reflection we can also find out about various methods associated with newly created object and how to use these object.
• To find out the attributes and methods associated with an object we can use the abstract class MemberInfo, this class is available under the namespace System.Reflection.

Add Check Box in Calender Control and Select WeekEnds on click of Button

Format Calender Controls :

Add Check Boxes manually in Calender Control and Select Week Ends on click of Button.

Code :

Partial Class SelectWeekEnds
    Inherits System.Web.UI.Page

    Dim btnclick As Boolean = False

    Protected Sub Calendar1_DayRender(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.DayRenderEventArgs) Handles Calendar1.DayRender
        Dim ctl As New CheckBox
        ctl.ID = "chk" & e.Day.Date.ToString.Substring(0, 10)
        If btnclick = True Then
            If CInt(e.Day.Date.DayOfWeek) = 0 Or CInt(e.Day.Date.DayOfWeek) = 6 Then
                ctl.Checked = True
            End If
        End If
        e.Cell.Controls.Add(ctl)
    End Sub

    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click
        btnclick = True
    End Sub

End Class

Add Check Box in Calender Control

Add Checkbox in Calender Control manually.

Code :

Partial Class SelectWeekEnds
  Inherits System.Web.UI.Page

  Protected Sub Calendar1_DayRender(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.DayRenderEventArgs) Handles Calendar1.DayRender
      Dim ctl As New CheckBox
      ctl.ID = "chk" & e.Day.Date.ToString.Substring(0, 10)
      e.Cell.Controls.Add(ctl)
  End Sub  

End Class

Regular Expression for Alphanumeric using Javascript

You can use Javascripts to validate this as followes.

Define the Javascript Function "isNumberEvt" on Head Section. and check it on keypress even of text box like "onkeypress="return isNumberEvt(event)"".

Javascript :

    function isNumberEvt(evt)
    {

        var charCode = (evt.which) ? evt.which : event.keyCode
        if ((charCode > 31 && charCode <> 57 && charCode <> 90 && charCode <> 122))
        return false;

        return true;

    }

aspx:

call function onkeypress="return isNumberEvt(event)" even of Textbox.

    asp:textbox id="TextBox1" onkeypress="return isNumberEvt(event)" runat="server" width="238px"

Check for Internet Connection availability in ASP. Net

Following code Check for Internet Connection availability in ASP. Net

Code :

Partial Class frmChkInternetConnection
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
        If fnChkInternetConn() Then
            Response.Write("Congrats ! Internet Connection is Available.")
        Else
            Response.Write("Sorry ! Internet Connection is not Available.")
        End If
    End Sub

    Public Function fnChkInternetConn() As Boolean
        Dim objreq As System.Net.HttpWebRequest
        Dim objres As System.Net.HttpWebResponse
        Try
            objreq = CType(System.Net.HttpWebRequest.Create("http://www.google.com"), System.Net.HttpWebRequest)
            objres = CType(objreq.GetResponse(), System.Net.HttpWebResponse)
            objreq.Abort()
            If objres.StatusCode = System.Net.HttpStatusCode.OK Then
                Return True
            End If
        Catch weberrt As System.Net.WebException
            Return False
        Catch except As Exception
            Return False
        End Try
    End Function
End Class

To Validate Only Digits Using JavaScript

Valdate Textbox to accept only Digits using Javascript.

Use this function on "keyup" event of Textbox.

Javascript:

    function isDigit(evt)
    {
        var charCode = (evt.which) ? evt.which : event.keyCode

        if (charCode > 47 && charCode < 58)
        { 
            return true;
        }
        else
        {   
            return false;
        }      
    }

aspx:

 asp:textbox id="TextBox1" onkeyup="return isDigit(event)" runat="server" width="238px" 

Validate the Maximum no. of Characters allowed in TextBox Using Java Script.

Function for Check and limit the number of characters allowed in a Textbox.

CheckLength(txt,5) : It will allow only 5 Characters in text box.

Javascript :

    function CheckLength(obj,Length)
    {
        if (obj.value.length>Length)
        {
            alert("Exceeding Maximum " + Length +" Characters")
            obj.focus()
            obj.select()
        }
    } 

aspx :

asp:textbox id="TextBox1" onkeyup="CheckLength(this,5)" runat="server" width="238px" 

To Validate Numbers Using JavaScript

Use the following function to Check the object does ahve a Numeric value or not.

javascript :

    function Validatenumber(obj)
    {
        if (obj.length !=0)
        {
            var text = /^[-0-9]+$/;

            if ((document.getElementById(obj.id).value != "") && (!text.test(document.getElementById(obj.id).value)))
            {
                alert("Please enter numeric values only");
                obj.focus();
                obj.select();
            }
        }
    }

For Validating the Year Value Using Javascript ...

The following code used to validate "Year" using javascript.

Javascript :

    function ValidateYear(obj)
    {
        if (obj.length !=0)
        {
            var text = /^[0-9]+$/;

            if ((document.getElementById(obj.id).value != "") && (!text.test(document.getElementById(obj.id).value)))
            {
                alert("Please Enter Numeric Values Only");
                obj.focus();
                obj.select();
            }

            if (document.getElementById(obj.id).value.length>4)
            {
                alert("Year is not proper. Please check");
                obj.focus();
                obj.select();
            }
        }
    }