?
Solved

DataColumn.MaxLength property always returns -1 ?

Posted on 2009-04-08
11
Medium Priority
?
1,066 Views
Last Modified: 2012-05-06
The client application receives the DataSet via a web service call.

Here is the code inside the web service that populates the dataset which is sent back to the client.
Dim DA As SqlDataAdapter
                Dim DS As New DataSet
                Cmd.CommandText = strSelect
                DA = New SqlDataAdapter(Cmd)
                DA.Fill(DS, "RunSQL")
                DA.Dispose()
                Con.Close()
                Return DS

Open in new window

0
Comment
Question by:tfsln
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
11 Comments
 
LVL 6

Expert Comment

by:HarryNS
ID: 24104005
Are you sure that dataset is getting filled up in your web service?

If so, then in your client application you can see the count of columns, DS.Tables[0].Columns.Count
0
 
LVL 9

Expert Comment

by:Sreedhar Vengala
ID: 24104007
What is your strSelect value ?
0
 
LVL 7

Expert Comment

by:Chandan_Gowda
ID: 24104088
check the dataset and make sure, the dataset is properly filled.
0
How to Create Failover DNS Record Sets in Route 53

Route 53 has the ability to easily configure DNS record sets specifically for failover scenarios. These failover record sets can be configured to failover to full-blown deployments in other regions or to a static HTML page that informs your customers of the issue.

 
LVL 15

Expert Comment

by:oobayly
ID: 24115263
What's the datatype of the column? According the MSDN, "The MaxLength property is ignored for non-text columns."
http://msdn.microsoft.com/en-us/library/system.data.datacolumn.maxlength(VS.80).aspx
0
 

Author Comment

by:tfsln
ID: 24128751
HarryNS: I dont want a column count, i want the max lengths for the columns in the dataset (as specified in the database table design)

The select query is, lets say, "Select * from tablename"

I am not trying to get the MaxLength of any other columns other than varchar (the db is sql server 2005).
0
 
LVL 15

Accepted Solution

by:
oobayly earned 2000 total points
ID: 24128999
Add the following line after you create the DataAdapter, it will tell the DataAdapter to fetch the table schema as well as the data

More information at:
http://msdn.microsoft.com/en-us/library/system.data.missingschemaaction.aspx
DA.MissingSchemAction = MissingSchemaAction.AddWithKey

Open in new window

0
 

Author Comment

by:tfsln
ID: 24133165
This doesnt seem to work when i use a complex query... Its sensitive information so i cant paste it, but are you aware of any limitations in using this property?

I often batch queries together to return multiple datatable's inside the dataset - is this a problem? Or using joins/unions?
0
 
LVL 15

Expert Comment

by:oobayly
ID: 24133312
To be quite honest, this isn't something I've ever used, so I can't say how multiple joins or returning multiple datasets will effect using the property.

However, just doing some simple testing, selecting multiple simple tables doesn't cause any issues and neither does a query that has a single inner join.
My only thought is that you may be returning composite fields, so the schema can't be returned.
0
 

Author Comment

by:tfsln
ID: 24133334
I do include composite fields... but i would have expected those fields to return the same value for MaxLength as any other field which doesnt have a max length (i.e. datetime)

If they do error, then thats a problem... Ill have to abandon this path
0
 
LVL 15

Expert Comment

by:oobayly
ID: 24133405
Interesting, I ran the following code and in all 5 tables returned the columns had the expected MaxLength properties set.
For the composite fields, the MaxLength property set was the Length of the longest string returned, whilst for the standard fields, MaxLength = 64 for a VARCHAR(64) field etc.
      SqlDataAdapter adapter= new SqlDataAdapter("SELECT * FROM tblVehicles;SELECT * FROM tblBodyTypes;"+
        "SELECT * FROM tblVehicles INNER JOIN tblBodyTypes ON tblVehicles.fldBodyID = tblBodyTypes.fldBodyID;" +
        "SELECT 'Foo' + ' ' + 'bar' AS [Foo];" +
        "SELECT fldModelDescription + 'Foo' AS [Foo] FROM tblVehicles", conn);
      adapter.MissingSchemaAction = MissingSchemaAction.AddWithKey;
      DataSet ds = new DataSet();
      adapter.Fill(ds);

Open in new window

0
 

Author Comment

by:tfsln
ID: 24133414
Interesting... Im going to need to run more tests. It logged in to our application but then failed on one of the most complex queries we have.

Its difficult, because when i test my web service it only allows me to enter text on one line - but i need to paste it a huge query over many lines just so that i can get the error message. At the moment we use the ASPAccelerator to compress web service output and a side effect is that all errors are returned as "Xml was not well formed"
0

Featured Post

On Demand Webinar: Networking for the Cloud Era

Did you know SD-WANs can improve network connectivity? Check out this webinar to learn how an SD-WAN simplified, one-click tool can help you migrate and manage data in the cloud.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This document covers how to connect to SQL Server and browse its contents.  It is meant for those new to Visual Studio and/or working with Microsoft SQL Server.  It is not a guide to building SQL Server database connections in your code.  This is mo…
For those of you who don't follow the news, or just happen to live under rocks, Microsoft Research released a beta SDK (http://www.microsoft.com/en-us/download/details.aspx?id=27876) for the Xbox 360 Kinect. If you don't know what a Kinect is (http:…
In this video you will find out how to export Office 365 mailboxes using the built in eDiscovery tool. Bear in mind that although this method might be useful in some cases, using PST files as Office 365 backup is troublesome in a long run (more on t…
How to fix incompatible JVM issue while installing Eclipse While installing Eclipse in windows, got one error like above and unable to proceed with the installation. This video describes how to successfully install Eclipse. How to solve incompa…
Suggested Courses

762 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question