>Bear in mind that I haven't touched VFP in 10+ years....
>
>I'm writing this:
>
>

>CLEAR
>sqlProcs = CREATEOBJECT("MyStuff ")
>sqlProcs.ConnectionString = "Data Source=192.168.2.5;Initial Catalog=Spares2;User Id=Kevin;Password=password1"
>
>LOCAL conneted as Boolean
>conneted = sqlProcs.TestConnection()
>
>IF sqlProcs.ErrorOccured
>	? sqlProcs.ErrorMessage
>ELSE
>	? conneted
>ENDIF
>
>
>
>#DEFINE TRUE	.T.
>#DEFINE FALSE	.F.
>#DEFINE NEWLINE CHR(13)
>
>DEFINE CLASS MyStuff AS Custom
>
>	connectionHandle = 0;
>
>	ErrorMessasge = ""
>	ErrorOccured = FALSE
>	
>	ConnectionString = ""
>	PROCEDURE ConnectionString_Access()
>    	RETURN This.ConnectionString 
>	ENDPROC
>
>	PROCEDURE ConnectionString_Assign(PropValue)
>    	This.ConnectionString   = PropValue
>	ENDPROC
>
>	**********************************************************
>	* Function.: TestConnection
>	* Purpose..: Tests a connnection to SQL Server
>	*
>	**********************************************************
>  	FUNCTION TestConnection() AS Boolean
>
>		LOCAL Connected AS Boolean
>		Connected = TRUE
>
>		IF This.ConnectionString = "" THEN
>			ErrorMessasge = "No connection string specified"
>			ErrorOccured = TRUE
>		ENDIF
>		
>		IF NOT ErrorOccured 
>			SQLSETPROP(0,"DispLogin",3)
>
>			TRY
>				connectionHandle = SQLSTRINGCONNECT(This.ConnectionString)
>			CATCH TO exceptionObject
>				AERROR(errorArray)
>		   		ErrorMessasge = "Error " + ALLTRIwM(STR(errorArray(0))) + ". Cannot make connection." + NEWLINE + errorArray(1)
>		   		ErrorOccured = TRUE
>				Connected = FALSE
>			ENDTRY
>				   
>			IF connectionHandle >0
>			   = SQLDISCONNECT(connectionHandle )
>			ENDIF
>			
>		ENDIF
>		
>	RETURN Connected
>
>
>ENDDEFINE
>

>
>When I run this, the connection string property is empty down in TestConnection
>
>What am I doing wrong here???

Modified version of your code:

CLEAR
sqlProcs = CREATEOBJECT("MyStuff")
sqlProcs.ConnectionString = "Data Source=192.168.2.5;Initial Catalog=Spares2;User Id=Kevin;Password=password1"

LOCAL conneted as Boolean
CLEAR

conneted = sqlProcs.TestConnection()

IF sqlProcs.ErrorOccured
    ? sqlProcs.ErrorMessage, sqlProcs.ConnectionString
ELSE
    ? conneted, sqlProcs.connectionHandle 
    
ENDIF



#DEFINE TRUE    .T.
#DEFINE FALSE    .F.
#DEFINE NEWLINE CHR(13)

DEFINE CLASS MyStuff AS Custom

    connectionHandle = 0;

    ErrorMessage = ""
    ErrorOccured = FALSE
    
    ConnectionString = ""
    PROCEDURE ConnectionString_Access()
        RETURN This.ConnectionString 
    ENDPROC

    PROCEDURE ConnectionString_Assign(PropValue)
        This.ConnectionString   = PropValue
    ENDPROC

    **********************************************************
    * Function.: TestConnection
    * Purpose..: Tests a connnection to SQL Server
    *
    **********************************************************
      FUNCTION TestConnection() AS Boolean

        LOCAL Connected AS Boolean
        

        IF This.ConnectionString == "" THEN
            this.ErrorMessage = "No connection string specified"
            this.ErrorOccured = TRUE
        ENDIF
        
        IF NOT this.ErrorOccured
            SQLSETPROP(0,"DispLogin",3)
            this.connectionHandle = SQLSTRINGCONNECT(This.ConnectionString)
            IF this.connectionHandle < 0
                AERROR(errorArray)
                this.ErrorMessage = "Error " + ALLTRIM(STR(errorArray[1])) +;
                                    ". Cannot make connection." + NEWLINE + errorArray(2)
                this.ErrorOccured = TRUE
            ELSE
                Connected = TRUE
            ENDIF
                   
            IF this.connectionHandle >0
               = SQLDISCONNECT(connectionHandle )
            ENDIF
            
        ENDIF
        
    RETURN Connected


ENDDEFINE