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Query an Access database using LinQ in Visual Basic 2012

Posted on 2014-04-29
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I am in a Visual Basic class learning about querying an Access database using LinQ.  And struggling.  I have an Access database.  I have added it as a datasource in my project.  Now I want to query the table and write the result to a variable.
The dataset name is Project3dbdataset.
The column names are Character, SkillLevel, Level, Score, and Damage

Here is my code:
Dim SL1 = From txtSkillLevel In Project3dbdataset
        Where Character = 7
        Select SkillLevel

It fails at Dim SL1 = From txtSkillLevel In Project3dbdataset
with error
Project3dbdataset is a type and cannot be used as an expression.

How do I access the dataset with the query?

Thanks,
Brooks
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Question by:gbnorton
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8 Comments
 
LVL 52

Expert Comment

by:Carl Tawn
ID: 40031434
The dataset contains (potentially) multiple tables, so you should be specifying DataSetName.SomeTableName.

Intellisense should be your friend here. If you still have trouble can you open your dataset designer and post a screengrab of it?
0
 

Author Comment

by:gbnorton
ID: 40032019
Intellisense  displays the dataset, but not the table name.  Attached is a screenshot of the dataset designer.
dataset-designer.jpg
0
 
LVL 52

Expert Comment

by:Carl Tawn
ID: 40032163
Just had a play around. It should be more like:
        Dim adap As New Project3dbdatasetTableAdapters.EvilCharactersTableAdapter()
        Dim table As New Project3dbdataset.EvilCharactersDataTable

        adap.Fill(table)

        Dim SL1 = From item In table
                    Where item.Character = 7
                    Select item.SkillLevel

Open in new window

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Author Comment

by:gbnorton
ID: 40032829
Almost there.  What is in SL1?  I tried to see it using:
Msgbox(SL1)

but get the error "Prompt cannot be converted to type string."

The column SkillLevel is type number.

I appreciate your help.
Brooks
0
 
LVL 52

Accepted Solution

by:
Carl Tawn earned 2000 total points
ID: 40034025
It will be type defined in the underlying database column. The syntax you have been using is using a Variant datatype.

You should also be able to use the following to make it explicitly numeric:
        Dim SL1 As Integer = From item In table
                    Where item.Character = 7
                    Select item.SkillLevel

Open in new window

Or, you could call ToString() on the existing SL1 to cast it to string for the message box call.
0
 

Author Comment

by:gbnorton
ID: 40042176
No joy.  Please take a look at the attachment.  
Thank you,
Brooks
Linq.jpg
0
 

Author Comment

by:gbnorton
ID: 40047250
Carl,
I've been reading and reading but unable to move forward.  Any ideas?
thanks,
Brooks
0
 

Author Closing Comment

by:gbnorton
ID: 40064949
I was not able to get this working but appreciate you looking at it.
0

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