@anasspir05 ,
In 1st case, when you select 'first value' in dropdown and content as "hello this is my " and click on Save, final content will become as "hello this is my first value" (you can refresh the console, so that this final value will get reflected in input form as well.)
And next time, when you select 'second value' in dropdown and with the same content for the same record and click on save, it will update as "hello this is my Second value" in schema (you can refresh the console, so that this new updated value will get reflected in input form as well.)
But if you want "hello this is my First Value Second value" after the above mentioned 2nd scenario, only way from input form is, you need to copy the final content and paste it in content, and then select the dropdown value.

Hi ,
THANK U @parthasarathy And @aggabhi for Your Help ,
I found the solution in fact it is the SOAP call, I have two input attributes and one output then what I do is that I create a function that processes all that and each time I click on a button that I put in my form bah it works, here is the code:
The Input forms :
<input xpath="message_content"/>
<input xpath="@AEnumeration"/>
<input label="Add" type="button">
<enter>
<soapCall name="setMessageContent" service="tst:concatainer">
<param exprIn="message_content" type="string"/>
<param exprIn="@AEnumeration" type="string"/>
<param type="string" xpathOut="message_content"/>
</soapCall>
</enter>
</input> And i Add this in my dataSchema :
<methods>
<method library="tst:concatainer.js" name="setMessageContent" static="true">
<parameters>
<param desc="message_content" inout="in" name="message_content" type="string"/>
<param desc="A Enumeration" inout="in" name="AEnumeration" type="string"/>
<param desc="The form" inout="out" name="self" type="string"/>
</parameters>
</method>
</methods>i create a javascript code "tst:concatainer.js" this is the code of the JS :
function tst_concatainer_setMessageContent(message_content,AEnumeration)
{
return message_content+" "+AEnumeration
}