How to create common event handler function to handle and respond to multiple buttons and perform the operations like sum, subtraction, multiplication and division

Introduction: In this article i am going to share the trick to calculate the operations like Sum, subtraction, multiplication and division on two numbers by creating a common event handler method in asp.net using both C# and VB languages.

Note: The real benefit of this is that we don't need to write the code on each button, we can create a single common function that handle and respond to all the buttons to perform their specific task.

Description: While working on asp.net project i was required to perform different calculation but without writing the code on each button so i searched on internet and after some efforts got the solution hint to create a common event handler function that can do the job.  So i created the common handler and going to share that will all so that developers can take the advantage of this.

In previous article i explained How to Evaluate mathematical/arithmetic string expression in asp.net and Show image preview before uploading through asp.net fileupload control using jQuery and Get age in years,months,days,hours and seconds from DOB and Convert Rupees,Currency or Numbers to Words and Bind state categories and cities sub categories in single dropdownlist and Get city, state and country based on zip code using Google map API and Generate random number in asp.net

Implementation: Let's create a simple web application to perform the operations like Sum, subtraction, multiplication and division on two numbers.

Asp.Net C# Section:

• Design the asp.net page (default.aspx) as:

<fieldset style="width: 400px;">

    <legend>Use of common handler in Asp.net C#</legend>   

    <table>

    <tr>

    <td>Enter First Number: </td>

    <td><asp:TextBox ID="txtFirstNum" runat="server"></asp:TextBox>   

    </td>

    </tr>

    <tr>

    <td>Enter Second Number: </td>

    <td><asp:TextBox ID="txtSecondNum" runat="server"></asp:TextBox></td>

    </tr>

    <tr>

    <td>Result: </td>

    <td><asp:TextBox ID="txtResult" runat="server"></asp:TextBox></td>

    </tr>

        <tr>

    <td>&nbsp;</td>

    <td>

    <asp:Button ID="btnSum" runat="server" onclick="Calculate" Text="Sum" />

        <asp:Button ID="btnSub" runat="server" onclick="Calculate" Text="Subtract" />

        <asp:Button ID="btnMul" runat="server" onclick="Calculate" Text="Multiply"/>

        <asp:Button ID="btnDiv" runat="server" onclick="Calculate" Text="Divide"/>

    </td>

    </tr>

    </table>       

   </fieldset>

Note: Have you noticed the highlighted part in above Html markup. All the button are calling the same event handler on click of button.

• Now its time to create the common event handler function so in the Code behind file (default.aspx.cs)  create a common function that will respond to all the buttons:

protected void Calculate(object sender, EventArgs e)

    {

        if (sender == btnSum)

        {

            txtResult.Text = Convert.ToString(Convert.ToInt32(txtFirstNum.Text) + Convert.ToInt32(txtSecondNum.Text));

        }

        else if (sender == btnSub)

        {

            txtResult.Text = Convert.ToString(Convert.ToInt32(txtFirstNum.Text) - Convert.ToInt32(txtSecondNum.Text));

        }

        else if (sender == btnMul)

        {

            txtResult.Text = Convert.ToString(Convert.ToInt32(txtFirstNum.Text) * Convert.ToInt32(txtSecondNum.Text));

        }

        else

        {

            txtResult.Text = Convert.ToString(Convert.ToInt32(txtFirstNum.Text) / Convert.ToInt32(txtSecondNum.Text));

        }

    }

Asp.Net VB Section

• Design the asp.net page (default.aspx) as:

<fieldset style="width:400px;">

    <legend>Use of common handler in Asp.net C#</legend>   

    <table>

    <tr>

    <td>Enter First Number: </td>

    <td><asp:TextBox ID="txtFirstNum" runat="server"></asp:TextBox></td>

    </tr>

    <tr>

    <td>Enter Second Number: </td>

    <td><asp:TextBox ID="txtSecondNum" runat="server"></asp:TextBox></td>

    </tr>

    <tr>

    <td>Result: </td>

    <td><asp:TextBox ID="txtResult" runat="server"></asp:TextBox></td>

    </tr>

        <tr>

    <td>&nbsp;</td>

    <td>

        <asp:Button ID="btnSum" runat="server" Text="Sum" />

        <asp:Button ID="btnSub" runat="server" Text="Subtract" />

        <asp:Button ID="btnMul" runat="server" Text="Multiply"/>

        <asp:Button ID="btnDiv" runat="server" Text="Divide"/>

    </td>

    </tr>ot

    </table>       

  </fieldset>

• In the Code behind file (default.aspx.cs)  write the code as:

Protected Sub btnSum_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnSum.Click, btnSub.Click, btnMul.Click, btnDiv.Click

        If sender Is btnSum Then

            txtResult.Text = Convert.ToInt32(txtFirstNum.Text) + Convert.ToInt32(txtSecondNum.Text)

        ElseIf sender Is btnSub Then

            txtResult.Text = Convert.ToInt32(txtFirstNum.Text) - Convert.ToInt32(txtSecondNum.Text)

        ElseIf sender Is btnMul Then

            txtResult.Text = Convert.ToInt32(txtFirstNum.Text) * Convert.ToInt32(txtSecondNum.Text)

        Else

            txtResult.Text = Convert.ToInt32(txtFirstNum.Text) / Convert.ToInt32(txtSecondNum.Text)

        End If

    End Sub

Note: The same button is handling the events of all the button

Now over to you:

" I hope you have got the trick to create common event handler function to handle and respond to multiple buttons in asp.net and If you like my work; you can appreciate by leaving your comments, hitting Facebook like button, following on Google+, Twitter, Linked in and Pinterest, stumbling my posts on stumble upon and subscribing for receiving free updates directly to your inbox . Stay tuned and stay connected for more technical updates."

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