Showing image from project folder to datagridview in C#

An exception of type 'System.IO.FileNotFoundException' occurred in System.Drawing.dll but was not handled in user code

Additional information: ~/images/pdf.png

void gvProduct_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
       {

           if (e.RowIndex > -1 && e.ColumnIndex == this.gvProduct.Columns["Calibrateimg"].Index)
           {
               if (this.gvProduct["CalibratCertificate", e.RowIndex].Value != null)
               {
                  // string s = this.gvProduct["CalibrationCertificate", e.RowIndex].Value.ToString();

                           string Calibaration = gvProduct.Rows[e.RowIndex].Cells["CalibratCertificate"].Value.ToString().Trim();
                           string targetPath = System.Windows.Forms.Application.StartupPath + "\\App_Data\\CalibrationCertificate\\";

                           string extn = Path.GetExtension(Calibaration);

                           // read the file data
                           switch (extn)
                           {
                               case ".pdf":
                            MessageBox.Show("test img");
                           e.Value = Image.FromFile("~/images/pdf.png");
                                   break;

                               case ".docs":
                                   e.Value = Image.FromFile("~/images/word.png");
                                   break;
                            }
               }

           }
       }

<pre> public void BindGrid()
        {
            DataSet ds = new DataSet();
            ds = BindData("BindProduct", this.branch, string.Empty);


            DataGridViewImageColumn img = new DataGridViewImageColumn();
            img.Name = "Calibrateimg";
            img.HeaderText = "Calibrateimg";

            if (ds.Tables[0].Rows.Count > 0)
            {
                gvProduct.AutoGenerateColumns = true;
                gvProduct.DataSource = ds.Tables[0];
                
                gvProduct.DataBindings.ToString();


                this.gvProduct.Columns.Add(img);
                this.gvProduct.Columns["CalibratCertificate"].Visible = false;

                this.gvProduct.CellFormatting += new DataGridViewCellFormattingEventHandler(gvProduct_CellFormatting);


                gvProduct.Refresh();
             
                
                
            }