Joe had a problem. He had a restricted folder from which he was allowing authorized downloading through a response.binarywrite. It is fairly straight forward stuff. But, he didn't want to write a big switch statement based on the various file extensions in order to determine the file type for the Response.ContentType = "xx" statement.

5 and a half hours later he answered his own question:

System.Runtime.InteropServices.DllImport("urlmon.dll", 
   CharSet = System.Runtime.InteropServices.CharSet.Unicode, 
   ExactSpelling = true, SetLastError = false)] 
static extern int FindMimeFromData(IntPtr pBC, 
   [System.Runtime.InteropServices.MarshalAs(
      System.Runtime.InteropServices.UnmanagedType.LPWStr)] string pwzUrl,
   [System.Runtime.InteropServices.MarshalAs(
      System.Runtime.InteropServices.UnmanagedType.LPArray, 
      ArraySubType = System.Runtime.InteropServices.UnmanagedType.I1, SizeParamIndex = 3)] 
   byte[] pBuffer, int cbSize,
   [System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.LPWStr)] 
   string pwzMimeProposed, int dwMimeFlags, out IntPtr ppwzMimeOut, int dwReserved);    
    
    /// <summary>
    /// Ensures that file exists and retrieves the content type 
    /// </summary>
    /// <param name="strfileName"></param>
    /// <returns>Returns the Content MimeType </returns>
    public static string getMimeFromFile(string strFileName)
    {
        IntPtr mimeout;
        if (!System.IO.File.Exists(strFileName))
            throw new System.IO.FileNotFoundException(strFileName + " not found");

        int MaxContent = (int)new System.IO.FileInfo(strFileName).Length;
        if (MaxContent > 4096) MaxContent = 4096;
        System.IO.FileStream fs = System.IO.File.OpenRead(strFileName);


        byte[] buf = new byte[MaxContent];
        fs.Read(buf, 0, MaxContent);
        fs.Close();
        int result = FindMimeFromData(IntPtr.Zero, strFileName, buf, 
           MaxContent, null, 0, out mimeout, 0);

        if (result != 0)
            throw System.Runtime.InteropServices.Marshal.GetExceptionForHR(result);

        string mime = System.Runtime.InteropServices.Marshal.PtrToStringUni(mimeout);
        System.Runtime.InteropServices.Marshal.FreeCoTaskMem(mimeout);
        return mime;
    }
    //rename crystal.jpg to .gif to test functionality!
    //string getImg = Environment.GetEnvironmentVariable("windir") 
    //   + "\\Web\\WallPaper\\Crystal.gif";
    //string mime = getMimeFromFile(getImg);

from a solution provided by Joe Johnston in Message #1167048

1) If you're using .NET 1.1, you can use the .GetSchemaTable() method of the DataReader class (either SqlDataReader or OleDbDataReader), as follows:

SqlCommand sc = new SqlCommand("select * from personnel", new SqlConnection(MyConnectionString));
sc.Connection.Open();
SqlDataReader drSql = sc.ExecuteReader(CommandBehavior.SchemaOnly);
DataTable test = drSql.GetSchemaTable();
sc.Connection.Close();

SqlConnection connection = new SqlConnection(MyConnectionString);
connection.Open();
DataTable test = connection.GetSchema("Columns", new string[] { null, null, "personnel" });
connection.Close();

from two solutions, provided by Çetin Basöz and Richard Hamm in Messages #1213367 and #1210023

from a solution provided by Rick Strahl in Message #1123792

You can't set anything that is set in the property sheet in the constructor. The constructor will be overridden by anything in InitalizeComponent(). If you move that code after the InitializeComponent() it should work.

Ideally you shouldn't do anything dynamic in the constructor at all - use Form_Load for those sort of things as it ensures that the form has properly initialized and all values have been set.

from a solution provided by Rick Strahl in Message #1233163