Setting all elements of an Array to Null in C# (like with memset in C++)

I sometime find it strange that things we take for granted in C++ are hard in C#. Probably I should say hard to find the equivalent for rather than hard to do. I routinely clear out my arrays in C++ with memset (setting each item to 0). To get the equivalent in C#, you can use the Array.Clear(...) method like this:

Array.Clear(MyArray,0,MyArray.Length);

Here is a more detailed example:

http://www.dotnetperls.com/array-clear

Preventing Flicker with GDI+ drawing in C#

In C#, the OnPaintBackground method is called before the OnPaint event and it draws the background color for the entire view. If you are already drawing the background in the OnPaint event, then this process will cause flicker. You can override the OnPaintBackground and just do nothing in it to prevent the flicker:

protected override void OnPaintBackground(PaintEventArgs pevent)
{
// do nothing
}

Script to Purge All Objects for a User in Oracle

I have to purge and reload an Oracle Database dump on a monthly basis. I have been manually deleting all of the Objects with Toad before loading the new dump. I searched for a script that would delete all of the objects. Many people suggested that you should just drop the user, but if I do this I have to add back in grants that don't get picked up by the export.

This thread on the Oracle Discussion Forum has several solutions. I am pasting the script that worked the best for me below from Massimo. There is some criticism in the thread about why he did not just use the object name in one case instead of all the If/Else conditions; however, I like this approach better, because I can easily take out something if I need to:

declare
stringa varchar2(100);

cursor cur is
      select  *
      from    user_objects;

begin
  for c in cur loop
    begin
      stringa := '';
      if c.object_type = 'VIEW' then
          stringa := 'drop view ' || c.object_name;
          EXECUTE immediate stringa;
      elsif c.object_type = 'TABLE' then
          stringa := 'drop table ' || c.object_name || ' cascade constraints';
          EXECUTE immediate stringa;
      elsif c.object_type = 'SEQUENCE' then
          stringa := 'drop sequence ' || c.object_name;
          EXECUTE immediate stringa;
      elsif c.object_type = 'PACKAGE' then
          stringa := 'drop package ' || c.object_name;
          EXECUTE immediate stringa;   
      elsif c.object_type = 'TRIGGER' then
          stringa := 'drop trigger ' || c.object_name;
          EXECUTE immediate stringa;   
      elsif c.object_type = 'PROCEDURE' then
          stringa := 'drop procedure ' || c.object_name;
          EXECUTE immediate stringa;
      elsif c.object_type = 'FUNCTION' then
          stringa := 'drop function ' || c.object_name;
          EXECUTE immediate stringa;     
      elsif c.object_type = 'SYNONYM' then
          stringa := 'drop synonym ' || c.object_name;
          EXECUTE immediate stringa;
      elsif c.object_type = 'INDEX' then
          stringa := 'drop index ' || c.object_name;
          EXECUTE immediate stringa;
      elsif c.object_type = 'PACKAGE BODY' then
          stringa := 'drop PACKAGE BODY ' || c.object_name;
          EXECUTE immediate stringa;  
      elsif c.object_type = 'DATABASE LINK' then
          stringa := 'drop database link ' || c.object_name;
          EXECUTE immediate stringa;  
      end if;
  exception
        when others then
        null;
    end; 
  end loop;
  -- PURGE recyclebin

end;
/

Convert char[] to String in c#

If you have something like:

char [] chArray = infile.ReadChars(10);

or

char[] chArray = new char[] {'t','e','s','t'};

and you want to convert it to a String, I always (incorrectly) try:

String str = chArray.ToString(); 

and it doesn't work (you get "System.Char[]").

You have to say something like this:

String str = new String(chArray);

Importing a Datapump export into Oracle with IMPDP

I never had to remember the command-line options for the old imp utility (because it prompted you for the info it needed), but with impdp, you need to know what to specify. Here is my simple example that works for me to import a Datapump export file:

impdp user/password schemas=mySchema dumpfile=myfile.dpdmp logfile=mylog.log

The schema parameter specifies which schema from the file to import.

The dumpfile parameter specifies the name of the datapump export file to import. The catch here is that the dump file location defaults to a default directory on the server (something like this):

c:\oracle\Administrator\admin\orcl\dpdump

You can change this path, but you have to create the directory in Oracle and specify it with a Directory Parameter. You have to create a directory in Oracle with something like this:

create directory MyExportDir as 'c:\exports';

Here is the detailed info for impdp on the Oracle site.

Creating a Tablespace in Oracle with SQL

I never can seem to remember the SQL to create a tablespace in Oracle. I am posting my example that I use to I can easily find it again in the future:

create tablespace MyTableSpaceName
logging
datafile 'MyTableSpaceFile.dbf'
size 32m
autoextend on
next 32m maxsize unlimited
extent management local;

Oracle Function to Read SDO_ORDINATE Values without causing Exception in .NET

Below is an Oracle function to read a specified SDO_ORDINATE value in an SDO_GEOMETRY attribute so that ODP.NET can handle them without causing an Arithmetic Overflow Exception in .NET when the Oracle NUMBER value has too many digits after the decimal place for a .NET Decimal value.

Most of this function comes from this thread on the Oracle Discussion Forum:

CREATE OR REPLACE function Get_Ordinate_Value(geom sdo_geometry, vPos number default 1) return number
  is
  begin

    if geom is null
    then
       return null;
    end if;

    if vPos <1 or vPos >geom.sdo_ordinates.count()
    then
      return null;
    end if;

    return round(geom.sdo_ordinates(vPos ),8);
  end;
/

Using the Function is something like this where I am getting the origin point and orientation vector for a 3D Oriented Point geometry:

select Get_Ordinate_Value(MyGeomAttr,1) as X,
        Get_Ordinate_Value(MyGeomAttr,2) as Y,
        Get_Ordinate_Value(MyGeomAttr,3) as Z,
        Get_Ordinate_Value(MyGeomAttr,4) as AngleX,
        Get_Ordinate_Value(MyGeomAttr,5) as AngleY,
        Get_Ordinate_Value(MyGeomAttr,6) as AngleZ
from MyTable

This function is pretty simple. I first check to see if the geometry attribute is Null and return Null if it is. I found that if I did not do this, you will get a geometry attribute that is Null passed into the function and you get a "ORA-06531: Reference to uninitialized collection" and it is sometimes hard to tell where it is coming from.

Then the index is checked to see that it is in range for the SDO_ORDINATE array.

I finally use the Round function to reduce the number of digits after the decimal point to a number that the .NET Decimal type can handle.