Forum Discussion

mugheessiddiqui's avatar
mugheessiddiqui
Contributor
8 years ago

Read Blob object from DB and convert to System.Collection.Generic.List type of object.

I have scenario where database field stores a System.Collection.Generic.List of Double object. Now I want to read a BLOB object from database field and convert it to list of Array or any type collect...
  • tristaanogre's avatar
    tristaanogre
    8 years ago

    Rather than "Value", you might want to use the GetChunk method.  What you'll need to do is get the ActualSize of the field and then use GetChunk to retrieve it.  I've not tested this but it might look something like this:

     rs.MoveFirst();
var blobSize = rs.Fields("slices").ActualSize;
  var blob = rs.Fields("slices").GetChunk(blobSize);
tristaanogre's avatar
tristaanogre
Esteemed Contributor

Rather than "Value", you might want to use the GetChunk method.  What you'll need to do is get the ActualSize of the field and then use GetChunk to retrieve it.  I've not tested this but it might look something like this:

 rs.MoveFirst();
var blobSize = rs.Fields("slices").ActualSize;
  var blob = rs.Fields("slices").GetChunk(blobSize);
mugheessiddiqui's avatar
mugheessiddiqui
Contributor
8 years ago

Thanks Now I have gotten Blob object.

 

Second Issue is to Cast the Blob object in some list/dictionary type object of JavaScript for traversing. As I told you we have stored blob object type of System.Collection.Generic.List of Double.

 

I have found the following description of System.Collection.Generic.List that takes the "<CLRType> collection" object. I don't know how to define <CLRType> collection object.

 

Description: System.Collection.Generic.List`1 zctor_3(<CLRType> collection);

 

So far code looks like and I get type Mismatch error.

 

rs.MoveFirst();

var blobSize = rs.Fields("slices").ActualSize;
var blob = rs.Fields("slices").GetChunk(blobSize);


var objList = Aliases.appName.AppDomain("appUI.exe").dotNET.System_Collections_Generic.List_1.zctor_3(blob); // Gives "Type Mismatch Error"

 

 

  • tristaanogre's avatar
    tristaanogre
    Esteemed Contributor
    8 years ago

    if your Blob is an image, it's not a collection.  A collection is an object that has fields and properties and items.  At least, that's my understanding.

     

    I don't know the specific collection object you are trying to use so I can't help you further.

    • mugheessiddiqui's avatar
      mugheessiddiqui
      Contributor
      8 years ago

      No Blob is not an image, it's an serialized object of System.Collections.Generic.List.

  • AlexKaras's avatar
    AlexKaras
    Champion Level 3
    8 years ago

    Hi,

     

    I am not absolutely sure, but I think that you should:

    -- Register relevant (system.dll?) .Net assembly in dotNet Bridge in TestComplete and

    -- Use something like

    var objList = dotNET.System_Collections_Generic.List_1.zctor_3(blob);

    in your code.

    As a result, objList variable should contain deserialized list of doubles that cannot be used 'as is' in your test code and must be converted to array or delimited string or something like that that can be iterated and used in JScript.

     

    • mugheessiddiqui's avatar
      mugheessiddiqui
      Contributor
      8 years ago

      System.Collection.Generic.List included in mscorlib.dll and it is already available in Test Complete.

      I think I have to deserialize the object but not sure how to do it.

      • AlexKaras's avatar
        AlexKaras
        Champion Level 3
        8 years ago

        Hi,

         

        As it was suggested by HKosova, you should figure-out what is returned from Blob - this may be some string/base64 encoded string/xml/etc. Then you should find corresponding List constructor and use it to deserialize the returning value.

        However, as it was also suggested by Helen, it may be easier/more convenient to create a simple .Net assembly with one function that will receive Blob ID and database connection string as input parameters, get Blob from the database, deserialize it and return the list as, say, CrLf-delimited string. I believe that you can easily get the above code from your developers.