DataTable does not contain definition for AsEnumerable

Asked 9/2, 2012 at 19:18 Answered 17/7, 2020 at 7:21

Using linq to query a datatable returns the following error: CS0117: 'DataSet1.map DataTable' does not contain a definition for 'AsEnumerable'

Project includes reference for System.Data.Datasetextensions.

Here's the code.

using System;
using System.Collections;
using System.ComponentModel;
using System.Configuration;
using System.Reflection;
using System.Data;
using System.Linq;
using System.Data.Linq;
using System.Data.Common;
using System.Data.DataSetExtensions;
using System.Linq.Expressions;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Data.SqlClient;

protected void Page_Load(object sender, EventArgs e)
    {
        var query1 = from mfg_nm in DataSet1.mapDataTable.AsEnumerable()

                     select mfg_nm;
}

running it w/out AsEnumerable() results in

var query1 = from mfg_nm in DataSet1.mapDataTable

                     select mfg_nm;

CS1660: Cannot convert lambda expression to type 'string' because it is not a delegate type.

Simian answered 9/2, 2012 at 19:18 Comment(1)

I think you forgot to accept an Answer as the right Answer. It helps. thanks – Suppletion 9/2, 2019 at 18:24

Add System.Data.DataSetExtensions from "nuget" or "add reference"

Add this code:

using System.Data.DataSetExtensions;

Hackett answered 4/6, 2019 at 6:49 Comment(0)

The method you want is in the System.Data namespace, so that using directive is fine, but you also need a reference to the System.Data.DataSetExtensions assembly. Are you sure you've got that reference as an assembly reference?

It's not clear why you've got a using directive for a System.Data.DataSetExtensions namespace - does that not raise an error?

What is the exact error with the AsEnumerable() call? (I'm surprised about the error you're getting with the second form... that's not the error I'd have expected.)

Namnama answered 9/2, 2012 at 19:21 Comment(20)

Thanks for the quick response. Removed System.data.datasetextensions. Confirmed System.data.datasetextensions assembly. Form web.config: <add assembly="System.Data.DataSetExtensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/> – Simian 9/2, 2012 at 20:8

@user1169290: Can you not just add it under references? I don't know whether having it under web.config makes a difference... – Namnama 9/2, 2012 at 20:10

that's how I added it,I think that added the lines to the config file – Simian 9/2, 2012 at 20:16

Compilation Error Description: An error occurred during the compilation of a resource required to service this request. Please review the following specific error details and modify your source code appropriately. Compiler Error Message: CS0117: 'DataSet1.BIA_device_dp_mapDataTable' does not contain a definition for 'AsEnumerable' Source Error: Line 32: protected void Page_Load(object sender, EventArgs e) Line 33: { Line 34: var query1 = from mfg_nm in DataSet1.BIA_device_dp_mapDataTable.AsEnumerable() Line 35: Line 36: select mfg_nm; – Simian 9/2, 2012 at 20:31

@user1169290: That's very strange - can you reproduce it in a short but complete console program? If you try DataTableExtensions.AsEnumerable(DataSet1.BIA_device_dp_mapDataTable) what does it show? – Namnama 9/2, 2012 at 20:34

I'm new to this, sorry if it's done incorrectly. I tried the following: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Data; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { DataTableExtensions.AsEnumerable(DataSet1.BIA_device_dp_mapDataTable); } } } And it returns "The name 'DataSet1' does not exist in the current context. Not sure what the issue is - I can bind to DataSet1 as an object data source – Simian 9/2, 2012 at 20:50

@user1169290: You'd have to actually have the data set available in your code. Did you try the other option I mentioned? – Namnama 9/2, 2012 at 21:20

just see the console question. what was the other option? – Simian 9/2, 2012 at 21:24

@user1169290: Calling what's normally an extension method explicitly: DataTableExtensions.AsEnumerable(DataSet1.BIA_device_dp_mapDataTable) – Namnama 9/2, 2012 at 21:26

I appreciate your persistence on this. Made this change to code and received the following errors. protected void Page_Load(object sender, EventArgs e) { var query = from mfg_nm in DataTableExtensions.AsEnumerable(DataSet1.BIA_device_dp_mapDataTable) select mfg_nm; } 'DataSet1.BIA_device_dp_mapDataTable' is a 'type', which is not valid in the given context The name 'DataSet1' does not exist in the current context – Simian 9/2, 2012 at 21:48

@user1169290: Okay, well that explains it. You're talking about a type, not an instance of the type. You need to actually have a DataTable to iterate over... – Namnama 9/2, 2012 at 22:3

I guess that's my confusion - if i have an instance that's populated with data, how do I create a datable to query? – Simian 10/2, 2012 at 16:38

@user1169290: The DataTable is the instance I'm talking about. It sounds like you should take a few steps back from LINQ for the moment, and work out how to get some data from whatever your original data source is first. – Namnama 10/2, 2012 at 17:14

the datatable has data. I can bind it to gridview or use objectdatasource and the they are populated with data. – Simian 10/2, 2012 at 17:49

@user1169290: But you don't have an instance, as far as we can see. DataSet1.BIA_device_dp_mapDataTable is a type (see the compiler error) so where's the instance? Maybe you've got some other variable, but you haven't shown it to us... – Namnama 10/2, 2012 at 17:51

FWIW, in VS2015, have added a reference to System.Data.DataSetExtensions in a WinForms project. At my using directive, using System.Data.DataSetExtensions, I get an Intellisense error that DataSetExtensions does not exist in System.Data, and in my code, myDataTable.asEnumerable is underscored in red, with an error that DataTable does not support any such method. I open the "potential fixes" up at the using directive, which offers me the option to "remove unnecessary", and I simply close the popup. The using directive becomes grayed out, and the error lower in the code disappears. – Mordy 9/5, 2017 at 12:48

But the project won't compile. Error CS0234 The type or namespace name 'DataSetExtensions' does not exist in the namespace 'System.Data' (are you missing an assembly reference?) – Mordy 9/5, 2017 at 12:49

@Tim: Well yes, as my answer says, having a using directive (not a using static, which would now be valid) for using System.Data.DataSetExtensions is invalid. DataSetExtensions is a class, not a namespace. Remove that using directive. But it's not clear whether you really do have a reference to the System.Data.DataSetExtensions assembly. Do you see it in the "References" part of Solution Explorer? – Namnama 9/5, 2017 at 13:19

Yes, the reference is valid, it is in Solution Explorer in the References section. I've removed the using directive. There's something screwy about my machine, I think. I've got the solution in a folder on Dropbox and it compiles at the office but not on my PC at home. I will reinstall the framework. – Mordy 9/5, 2017 at 16:58

Adding a namespace System.Data in View worked for me – Conventional 11/7, 2017 at 18:34

Add System.Data.DataSetExtensions from "nuget" or "add reference"

Add this code:

using System.Data.DataSetExtensions;

Hackett answered 4/6, 2019 at 6:49 Comment(0)

I got this error message: 'System.Data.DataTable' does not contain a definition for 'AsEnumerable' and no extension method 'AsEnumerable' accepting a first argument of type 'System.Data.DataTable' could be found (are you missing a using directive or an assembly reference?)

Added

using System.Data;

Added "System.Data.DataSetExtensions" to the References section. It resolved the problem.

Onstage answered 29/8, 2018 at 8:44 Comment(1)

This works. for some reason no question is accepted as the right answer. thanks – Suppletion 9/2, 2019 at 18:27

In all cases where this happens, the reference to System.Data.DataSetExtensions.dll was missing. If in doubt, try creating a simple console project targeting .NET 4 with a reference to System.Data.DataSetExtensions.dll, to verify that adding the reference actually works.

Also note that you only need to use the System.Data namespace.

BTW mapDataTable is a DataTable, right?

Arnaldo answered 9/2, 2012 at 19:27 Comment(1)

Yes, mapdatatable is a datatable – Simian 9/2, 2012 at 20:17

Google search "system.data.datatable does not contain a definition for asenumerable" brought me here, and my trouble was missing:

using System.Data;

Due to my implement the error message was a bit misleading. Hence, my answer to this question. Code was like...

public List<mytype> MyMethod(params) {
   return new mynamespace.myclasslib.myclass().GetDataTable(params).AsEnumerable()
      .etc
}

Once I tried to explicitly declare the DataTable, it became obvious that I was missing the using statement.

Schema answered 8/1, 2016 at 16:5 Comment(1)

Just want to add we also should have System.Linq – Flourish 10/5, 2017 at 14:53

Try this code :

DataSet1.mapDataTable.Select().AsEnumerable()

Swab answered 17/7, 2020 at 7:21 Comment(1)

Please provide some reasoning / explanation why do you think your solution is the appropriate approach. – Trihedron 17/7, 2020 at 7:36

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