Get File Names of a Particular File Type using LINQ

This is a simple trick to find File Names of a particular File Type existing in a Folder.

Background

Suppose you want to find the File Names of the CSV Files in a folder. So, you need to exclude all other files and consider the CSV Files only. This was implemented in one of my projects, where all the CSV File Names from a folder got populated in a DropDownList.

Let’s Explore

So, the main thing here is to find a particular type of File. For that, I used the following code:

DirectoryInfo di = new DirectoryInfo(folderPath);

// Get only the CSV files.
List<string> csvFiles = di.GetFiles("*.csv")
                          .Where(file => file.Name.EndsWith(".csv"))
                          .Select(file => file.Name).ToList();

Here, I have used DirectoryInfo.GetFiles Method (String).

Returns a file list from the current directory matching the given search pattern.

So, di.GetFiles(“*.csv”) would give us a list of all the CSV Files in that folder.

• Here *.csv is the SearchPattern and * means any string before .csv.
• Now, Where Clause is used to make sure that File Extension ends with .csv and nothing else.

Then, we are selecting the File Names by Select clause like Select(file => file.Name).

Note

You can apply this trick to find any File Type. You just need to change the SearchPattern accordingly. If you wish to find pdf files, then it would be di.GetFiles("*.pdf").

Full Code

I have used another Where condition here as per the requirements to exclude the CSV Files, having _something in their File Names.

/// <summary>
/// This function Populates CSV File Names on a DropDownList.
/// </summary>
private void PopulateCSVFilesDropDownList()
{
    try
    {
        string folderPath = GetFolderPath();

        if (!string.IsNullOrEmpty(folderPath))
        {
            if (Directory.Exists(folderPath))
            {
                DirectoryInfo di = new DirectoryInfo(folderPath);

                // Get only the CSV files excluding the ones having 
                // "_something" appended to them.
                List<string> csvFiles = di.GetFiles("*.csv")
                                          .Where(file => file.Name.EndsWith(".csv") &&
                                                         !file.Name.Contains("_something"))
                                          .Select(file => file.Name).ToList();

                // Bind the DropDown and add one default option at the top.
                ddlCSVFiles.DataSource = csvFiles;
                ddlCSVFiles.DataBind();
                ddlCSVFiles.Items.Insert(0, new ListItem("Please select a file", "-1"));
            }
            else
            {
                // DropDownList is hided and Error message is displayed.
                ddlCSVFiles.Visible = false;
                lblErrorMessage.Visible = true;
                lblErrorMessage.Text = "Folder Does not Exist.";
            }
        }
    }
    catch (Exception ex)
    {
        // Exception is displayed on a Label.
        lblErrorMessage.Visible = true;
        lblErrorMessage.Text = ex.Message;
    }
}

/// <summary>
/// This function returns the Folder Path from web.config, 
/// which contains different type of Files. 
/// </summary>
/// <returns>string: Folder Path</returns>
private string GetFolderPath()
{
    // For Example - D:\Projects\SomeProject\SomeFolder
    return (ConfigurationManager.AppSettings != null && 
            ConfigurationManager.AppSettings["FolderPath"] != null) ?
            ConfigurationManager.AppSettings["FolderPath"].ToString() :
            string.Empty;
}

Update

• 27^th February, 2014 - Added an extra condition in LINQ to check if File Name ends with .csv only and nothing else

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