Tag Archives: C#

Read Excel files using C-Sharp windows application

This article explains how to read excel files using c sharp in windows applications.

using System.Data.OleDb;

private void btnRead_Click(object sender, EventArgs e)
string connStr = connStr = “Provider=Microsoft.Jet.OLEDB.4.0;Data Source=” + Application.StartupPath + @”\Courier.xls;Extended Properties=ImportMixedTypes=Text;Excel 8.0;HDR=Yes;IMEX=1;”;

//You must use the $ after the object you reference in the spreadsheet
OleDbDataAdapter adap = new OleDbDataAdapter(“SELECT * FROM [Sheet1$]”, connStr);

DataSet ds = new DataSet();
adap.Fill(ds, “Courier”);
dataGridView1.DataSource = ds.Tables[“Courier”].DefaultView;

catch (Exception ex)

Explanation of the above code:
Here I used OleDb to read the excel file. The excel file resides with exe file as Courier.xls.

Sheet1$ is the name of excel sheet.
Courier is the name of file so i am using the same name in filling the DataSet.

Now at last the data is filled into dataGridView.

Now if you are not able to read the integer value or any value other then text then
include the
Extended Properties=ImportMixedTypes=Text;Excel 8.0;HDR=Yes;IMEX=1 property in connection string.

The above code can also be used in a web application, for this you need to replace the Application.StartupPath with Server.MapPath

HaPpY CoDiNg………..


Traverse / Loop through all form controls in asp.net

This post explains that how to traverse (loop through) all form controls in asp.net page.

foreach (System.Web.UI.Control ctrl in this.form1.Controls)
//here your code

Further if you want to get the state or data or manipulate the control, use the below code:
Here I am checking that at least one DropDownList item is selected out of all DropDownLists in the current webform.

bool isSelected = false;

foreach (System.Web.UI.Control ctrl in this.form1.Controls)

if (ctrl.GetType() == typeof(System.Web.UI.WebControls.DropDownList))
DropDownList ddl = (DropDownList)ctrl;

if (ddl.SelectedItem.Text != "")
isSelected = true;


if (isSelected == true)
Response.Write("none selected");

Username Regex Validation

While accepting values from user you must validate the values because wrong values (like XSS attacks) can cause harm to your database and website.

Regex Code:
The Regular Expression below validates the username format.

So while creating a new user for a website you can validate the username string with the following business logic:
1) User name must be between 5 to 20 characters.
2) User name can have lowercase and uppercase characters.
3) User name can be alpha-numeric.
4) No special character allowed.

As you can see this is a very basic code to evaluate simple username for your website.

Asp.net HTML code:

<asp:TextBox ID=”txtRegex” runat=”server”></asp:TextBox>
<asp:Button ID=”btnValidate” runat=”server” Text=”Validate value” OnClick=”btnValidate_Click” />
<asp:Label ID=”lblResultRegex” runat=”server” Text=””></asp:Label></div>

Asp.net Code Behind:

using System.Text.RegularExpressions;

protected void btnValidate_Click(object sender, EventArgs e)
    if (Regex.IsMatch(txtRegex.Text, @”^[a-zA-Z0-9_]{3,16}$”) == true)
        lblResultRegex.Text = “username ok”;
        lblResultRegex.Text = “username invalid”;

Now just run the application an verify the results.

To download a visual studio source code visit http://dotnetcoderoom.blogspot.com/2008/10/username-regex-validation.html

Read & Write to System Registry data, keys using C#

In this post i am going to explain that how to access the System Registry and how to read and write data to registry.

Step 1: First you need to import the below namespaces:
using Microsoft.Win32;

Step 2: Now create an object of Registry class:
RegistryKey regkey;

Step 3: Now access the registry and get the value of a key

regkey = Registry.CurrentUser.CreateSubKey(@”Software\Microsoft\FTP”);

if (regkey.GetValue(“Use PASV”) == null)
txtValue.Text = “No Value Specified”;

txtValue.Text = regkey.GetValue(“Use PASV”).ToString();

The above code gets the value of the “Use PASV” key from the
Registry\CurrentUser\Software\Microsoft\FTP path.

Step 4: Set the key value
regkey.SetValue(“Use PASV”, txtValue.Text);

Operator + cannot be applied to operands of type string and method group, C# error


This error comes up when you tries to append two strings with the “+” sign. As the + sign in C# is a arithmetical operator so you cannot use this too append two string type values. To use “+” the values or variables must be if numeric type.

As C# uses doesn’t supports implicit typecasting, for string concatenation use “&” sign.

string varTest = “”;
string str1 = “abc”;
int str2=21;

varTest = str1 + str2;

The above stqatmet will cause in error stating “Operator + cannot be applied to operands of type string and method group“. Because we are trying to add a string variable in a numeric variable.

To remove the error you must convert all the numeric (integer) datatype or variables to string.

varTest = str1 & str2.ToString();

The output of the above code will be abc21

We must convert all values to a uniform datatype before storing them into a variable.

Send e-mail in ASp.Net 2.0 and onwards in C#

The following code example can be used to send email using Asp.Net in 2.0 and higher versions version.

The Namespace of email class is changed to System.Net.Mail from System.Web.Mail.

Import the System.Net.Mail Namespace
using System.Net.Mail;


MailMessage mail = new MailMessage();
mail.From = new MailAddress(“info@yourDomain.com”,”Alert”);
mail.Subject = “mail test”;
mail.IsBodyHtml = true;
mail.Body = “Your message here”;
SmtpClient smtp = new SmtpClient(“mail.yourdomain.com”);
smtp.Credentials = new System.Net.NetworkCredential(“info@yourdomain.com”,”password of this info”);

The email address specified in the “FROM” field must be valid and it need to be of your domain.
In the SmtpServer the domain name must be same as of your domain on which website is hosted.

For complete source code visit

Send e-mail using Asp.Net 1.1

The following code example can be used to send email using Asp.Net in 1.1 version.

First import Web.Mail namespace.
using System.Web.Mail;

Now add this code to your button click event:

MailMessage mail = new MailMessage();

String msgText = string.Empty;
msgText = “Message here, you can also use Html tags for Rich Text Formatting.<br>Hi.”;

mail.To = “you@yourdomain.com”;
mail.CC = “anyEmailAddress, its optional”;
mail.Bcc = “anyEmailAddress, its optional”;
mail.From = @”””Ajay”” <info@yourdomain.com>”;
//mail.From = “info@yourdomain.com”;
mail.Subject = “Mail test”;
mail.BodyFormat = MailFormat.Html;
mail.Body = msgText;
SmtpMail.SmtpServer = “mail.yourdomain.com”;



The email address specified in the “FROM” field must be valid and it need to be of your domain.
In the SmtpServer the domain name must be same as of your domain on which website is hosted.