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   <TITLE>Add, delete, and modify BDE aliases from code</TITLE>

   <META NAME="Author" CONTENT="Harold Howe">

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<H3> Add, delete, and modify BDE aliases from code </H3>

<P> The VCL <TT>TSession</TT> class provides methods for adding, deleting, and

modifying BDE aliases. The functions are <TT>AddAlias</TT>, <TT>AddStandardAlias</TT>,

<TT>DeleteAlias</TT>, and <TT>ModifyAlias</TT>. The code example below demonstrates how to

use each one.

</p>

<pre>

<font color="navy">//-----------------------------------------------------------------</font>

<font color="navy">//  ModifyAlias</font>

<b>void</b> <b>__fastcall</b> TForm1<b>:</b><b>:</b>btnModifyClick<b>(</b>TObject <b>*</b>Sender<b>)</b>

<b>{</b>

    std<b>:</b><b>:</b>auto_ptr&lt; TStringList <b>></b> params<b>(</b> <b>new</b> TStringList<b>)</b><b>;</b>

    params<b>-></b>Values<b>[</b><font color="blue">"ENABLE BCD"</font><b>]</b> <b>=</b> <font color="blue">"TRUE"</font><b>;</b>

    Session<b>-></b>ModifyAlias<b>(</b><font color="blue">"BCDEMOS"</font><b>,</b> params<b>.</b>get<b>(</b><b>)</b><b>)</b><b>;</b>

    Session<b>-></b>SaveConfigFile<b>(</b><b>)</b><b>;</b>

<b>}</b>

<font color="navy">//-----------------------------------------------------------------</font>

<font color="navy">// AddStandardAlias</font>

<b>void</b> <b>__fastcall</b> TForm1<b>:</b><b>:</b>btnAddStandardClick<b>(</b>TObject <b>*</b>Sender<b>)</b>

<b>{</b>

    <b>const</b> AnsiString path <b>=</b>

        <font color="blue">"C:\\Program Files\\Common Files\\Borland Shared\\Data"</font><b>;</b>

    Session<b>-></b>AddStandardAlias<b>(</b><font color="blue">"BCBDEV_DB"</font><b>,</b> path<b>,</b> <font color="blue">"PARADOX"</font><b>)</b><b>;</b>

    Session<b>-></b>SaveConfigFile<b>(</b><b>)</b><b>;</b>

<b>}</b>

<font color="navy">//-----------------------------------------------------------------</font>

<font color="navy">// AddAlias</font>

<b>void</b> <b>__fastcall</b> TForm1<b>:</b><b>:</b>btnAddClick<b>(</b>TObject <b>*</b>Sender<b>)</b>

<b>{</b>

    std<b>:</b><b>:</b>auto_ptr&lt; TStringList <b>></b> params<b>(</b> <b>new</b> TStringList<b>)</b><b>;</b>

    params<b>-></b>Values<b>[</b><font color="blue">"ENABLE BCD"</font><b>]</b>    <b>=</b> <font color="blue">"TRUE"</font><b>;</b>

    params<b>-></b>Values<b>[</b><font color="blue">"DATABASE NAME"</font><b>]</b> <b>=</b> <font color="blue">"production"</font><b>;</b>

    params<b>-></b>Values<b>[</b><font color="blue">"SERVER NAME"</font><b>]</b>   <b>=</b> <font color="blue">"NTS_PROD"</font><b>;</b>

    params<b>-></b>Values<b>[</b><font color="blue">"USER NAME"</font><b>]</b>     <b>=</b> <font color="blue">"hhowe"</font><b>;</b>

    params<b>-></b>Values<b>[</b><font color="blue">"PASSWORD"</font><b>]</b>      <b>=</b> <font color="blue">"mfcblowschunks"</font><b>;</b>



    Session<b>-></b>AddAlias<b>(</b><font color="blue">"BCBDEV_SQL"</font><b>,</b> <font color="blue">"MSSQL"</font><b>,</b> params<b>.</b>get<b>(</b><b>)</b><b>)</b><b>;</b>

    Session<b>-></b>SaveConfigFile<b>(</b><b>)</b><b>;</b>

<b>}</b>

<font color="navy">//-----------------------------------------------------------------</font>

<font color="navy">// DeleteAlias</font>

<b>void</b> <b>__fastcall</b> TForm1<b>:</b><b>:</b>btnDeleteClick<b>(</b>TObject <b>*</b>Sender<b>)</b>

<b>{</b>

    Session<b>-></b>DeleteAlias<b>(</b><font color="blue">"BCBDEV_DB"</font><b>)</b><b>;</b>

    Session<b>-></b>SaveConfigFile<b>(</b><b>)</b><b>;</b>

<b>}</b>

<font color="navy">//-----------------------------------------------------------------</font>

</pre>

<P>

<H4>

ModifyAlias

</H4>

<P>

The first <TT>OnClick</TT> handler uses <TT>ModifyAlias</TT> to alter the <TT>BCDEMOS</TT> alias that comes with

C++Builder. <TT>ModifyAlias</TT> takes two parameteters. The first is an <TT>AnsiString</TT> that contains the

name of the alias that you want to modify. The second argument is a stringlist that contains the alias parameters that

you want to change. You don't have to list all of the available parameters for a given alias. You only have to list

parameters that you want to change. Any parameter that you omit will remain unchanged.

</P>

<P>

The stringlist should be formatted like this:

</P>

<PRE>

Property=Value

</PRE>

<P>

For example, the example code sets the "Enable BCD" property of the alias to true. In order to set this property, the

stringlist should contain this:

</p>

<PRE>

ENABLE BCD=TRUE

</PRE>

<P>

Case sensitivy does not matter. The easiest way to format a <TT>TStringList</TT> this way is to use the <TT>Values</TT>

array property. The <TT>Values</TT> property allows you to treat the stringlist as an assortment of properties and their

values. It's great for reading config files or INI files. It also makes it easy to work with the <TT>Params</TT>

property of <TT>TDatabase</TT>. One nice feature of the <TT>Values</TT> property is that it is smart enough to know

whether it should add a string to the list, or just modify an existing line.

</P>

<P>

After we call <TT>ModifyAlias</TT>, there is still more work to be done. <TT>ModifyAlias</TT> only changes the BDE

settings for the current BDE session. The changes are not saved permanently to the alias. In order to save the changes

permanently, we need to call the <TT>SaveConfigFile</TT> method of <TT>TSession</TT>. Notice that each <TT>OnClick</TT>

handler calls <TT>SaveConfigFile</TT>.

</P>

<H4>

AddStandardAlias

</H4>

<P>

The <TT>AddStandardAlias</TT> member of <TT>TSession</TT> allows you to add a Paradox, dBase, or ASCII alias.

<TT>AddStandard</TT> takes three arguments. The first is the name of the alias to create. This string must be unique.

The second parameter is the path to the database. The example code sets the directory to the same directory where the

BCB sample database resides. The last argument determines which driver the alias will use: Paradox, dBase, or ASCII. The

thrird argument should contain one of these strintgs.

</P>

<UL>

<LI> PARADOX

<LI> DBASE

<LI> ASCIIDRV

</UL>

<P>

<TT>AddStandardAlias</TT> does not allow you to pass a stringlist of paramaters. Call the <TT>ModifyAlias</TT> if you want to

modify a standard alias after creating it.

</p>

<H4>

AddAlias

</H4>

<P>

<TT>AddAlias</tt> adds a new SQL links alias to the BDE. You pass it the name of the alias, the driver to use, and a

stringlist that contains the alias parameters. The code example creates a new alias called BCBDEV_SQL. The alias uses

SQL links driver for MS Sql Server.

</P>

<H4>

DeleteAlias

</H4>

<P>

<TT>DeleteAlias</TT> is the simplest of the four functions to understand. You simply pass it the name of the alias to

delete. After calling <TT>DeleteAlias</TT>, you must call the <TT>SaveConfigFile</TT> method in order to make the

changes permanent.

</P>

<H4>

Notes

</H4>

<P>

These member functions of <TT>TSession</TT> are simply wrappers for the BDE api. The code for the FAQ could be

rewritten to use the BDE directly without even messing with <TT>TSession</TT>.

</P>

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<TR> <TD colspan = 2><B>Downloads for this FAQ</B> </TD> </TR>

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