Validate and upload image files in asp.net

Introduction: In previous articles i explained How to resize image in Asp.net and How to create thumbnail, small and large version of the uploaded image in Asp.net.  It is always better to validate the file extension before uploading file i.e. you want that user can upload only the files that you want e.g. if you want the user can upload only .jpg, .jpeg, .png, .gif , .bmp files then you have to write the code that can check the extension of the file the user is going to upload. Here is the way:

• Place a FileUpload control and a button control on design page(.aspx)

<asp:FileUpload ID="FileUpload1" runat="server" />

        <asp:Button ID="btnUploadImage" runat="server" Text="upload Image"

            onclick="btnUploadImage_Click"  />

C#.Net Code to Validate and upload image files in asp.net

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

    private bool IsValidExtension(string filePath)

    {

        bool isValid = false;

        string[] fileExtensions = {".bmp",".jpg",".png",".gif",".jpeg",".BMP",".JPG",".PNG",".GIF",".JPEG"};

        for (int i = 0; i <= fileExtensions.Length - 1; i++)

        {

            if (filePath.Contains(fileExtensions[i]))

            {

                isValid = true;

            }

        }

        return isValid;

    }

    protected void btnUploadImage_Click(object sender, EventArgs e)

    {

        if (IsValidExtension(FileUpload1.PostedFile.FileName))

        {

            //write code to upload file

            string filePath = (Server.MapPath("Uploads/") + Guid.NewGuid() + FileUpload1.PostedFile.FileName);

            FileUpload1.SaveAs(filePath);

        }

        else

        {

            Response.Write("Please upload .jpeg,.png,.gif,.jpg,.bmp image only");

        }

    }

VB.Net Code to Validate and upload image files in asp.net

• In the code behind (.aspx.vb) file write the code:

Private Function IsValidExtension(ByVal filePath As String) As Boolean

        Dim isValid As Boolean = False

        Dim fileExtensions As String() = {".bmp", ".jpg", ".png", ".gif", ".jpeg", ".BMP", _

         ".JPG", ".PNG", ".GIF", ".JPEG"}

        For i As Integer = 0 To fileExtensions.Length - 1

            If filePath.Contains(fileExtensions(i)) Then

                isValid = True

            End If

        Next

        Return isValid

    End Function

    Protected Sub btnUploadImage_Click(ByVal sender As Object, ByVal e As EventArgs)

        If IsValidExtension(FileUpload1.PostedFile.FileName) Then

            'write code to upload file

            Dim filePath As String = (Server.MapPath("Uploads/") + Guid.NewGuid() + FileUpload1.PostedFile.FileName)

            FileUpload1.SaveAs(filePath)

        Else

            Response.Write("Please upload .jpeg, .png, .gif, .jpg, .bmp image only")

        End If

    End Sub

 Note: In this example Uploaded file will be saved in the Uploads folder. You can create a folder with different name and Replace the Uploads folder with the name of your Folder.

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