Cannot delete file in C#.net windows application

Question

I am first creating Bitmap image file and saving it to some temp location. Later using that file to read in BitmapImage object to compare it with other file. Once comparison is done, I want to delete file but then it throws exception that file is being used by another process. How can I delete this file?

Here is my code:

private void btnLogin_Click(object sender, EventArgs e)
{
        string strPath = AppDomain.CurrentDomain.BaseDirectory;
        GC.Collect();

        if (txtLoginImage.Text != "")
        {
            string strFileName = txtLoginImage.Text.Substring(txtLoginImage.Text.LastIndexOf('\\') + 1);
            Bitmap MainImg = new System.Drawing.Bitmap(txtLoginImage.Text);

            Bitmap NewImage = ConvertToGrayScale(MainImg);

            NewImage.Save(AppDomain.CurrentDomain.BaseDirectory + "\\Images\\Temp\\" + strFileName, System.Drawing.Imaging.ImageFormat.Bmp);
            NewImage.Dispose();

            Uri SourceUri = new Uri(AppDomain.CurrentDomain.BaseDirectory + "\\Images\\Temp\\" + strFileName);
            BitmapImage source = new BitmapImage();

            source.UriSource = SourceUri;

            IrisSystem.Class.BLL.User_BLL ubll = new IrisSystem.Class.BLL.User_BLL();
            DataSet dsUserData= ubll.getlist();

            bool isMatchFound = false;

            if (dsUserData != null && dsUserData.Tables.Count > 0)
            {
                foreach (DataRow item in dsUserData.Tables[0].Rows)
                {
                    Uri TargetUri = new Uri(AppDomain.CurrentDomain.BaseDirectory + "\\Images\\Grayscale\\" + item["GrayScaleImgName"]);
                    BitmapImage Target = new BitmapImage(TargetUri);

                    if (source.IsEqual(Target))
                    {
                        IrisSystem.frmHome frm= new IrisSystem.frmHome();
                        frm.strFullName = item["FullName"].ToString();
                        frm.ShowDialog();
                        Form.ActiveForm.Close();
                        isMatchFound = true;
                        break;
                    }
                    Target = null;
                }

                if (!isMatchFound)
                    MessageBox.Show("Invalid Credential..","Invalid Operation");
            }
            File.Delete(AppDomain.CurrentDomain.BaseDirectory + "\\Images\\Temp\\" + strFileName);
        }
        else
            MessageBox.Show("Please select image", "Login Error");
    }

Answer 1

You need to make sure that your Bitmap objects are disposed properly.

You are not disposing the MainImg object. you need to use using {} block to make sure that objects are disposed properly.

Replace This:

Bitmap MainImg = new System.Drawing.Bitmap(txtLoginImage.Text);    
Bitmap NewImage = ConvertToGrayScale(MainImg);    
NewImage.Save(AppDomain.CurrentDomain.BaseDirectory + "\\Images\\Temp\\"
                         + strFileName, System.Drawing.Imaging.ImageFormat.Bmp);
NewImage.Dispose();

With This:

using(Bitmap MainImg = new System.Drawing.Bitmap(txtLoginImage.Text))            
using(Bitmap NewImage = ConvertToGrayScale(MainImg))
{
  NewImage.Save(AppDomain.CurrentDomain.BaseDirectory + "\\Images\\Temp\\" + 
                     strFileName, System.Drawing.Imaging.ImageFormat.Bmp);      
}

EDIT:

Replace This:

BitmapImage source = new BitmapImage();
source.UriSource = SourceUri;

With This:

BitmapImage source = new BitmapImage();
source.BeginInit();
source.UriSource = SourceUri;
source.EndInit();