Question

Get Data from a Datatable in C# using LINQ

Asked by: FLOG51

Hi

I have a Datatable "dt" from a third party SOAP call, and I wish to get ALL the Row data where a Field value = "some_value" and then use the data to fill a string query to update my MySQL database.

I have been on 100 different sites Stating syntax for LINQ and have not as yet been successful in finding a statement that selects ALL field data for a row in Datatable that meets the query criteria.

I have written some code below but am stuck on the Select all and ouput statement.

I am attempting to output the code to a Console to test the syntax.

I am not sure that I can use LINQ to MySQL yet, however all the update MySQL query code is OK so just need the LINQ logic

Thanks

FLOG51

public void testLINQ(DataTable dt)
        {
            IEnumerable<DataRow> rowInfo = dt.AsEnumerable();
 
            var allTableInfo = from tableInfo in rowInfo 
                where
                tableInfo.Field<string>("Status").Contains("PENDING")
                select *
                Console.WriteLine
        }

                                  
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Select allOpen in new window

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Asked On
2009-09-16 at 05:03:41ID24735973
Tags

LINQ

,

C#

,

Datatable

Topics

C# Programming Language

,

Language Integrated Query - LINQ

Participating Experts
3
Points
500
Comments
12

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Answers

 

by: daryalPosted on 2009-09-16 at 05:13:19ID: 25344689

Hello,
Do you need something like;

var allTableInfo = from o in dt
                           where o.Status== "PENDING"
                           select o;
                                              
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by: robkolskyPosted on 2009-09-16 at 05:17:40ID: 25344720

So, if I'm understanding you correctly, you want to find all rows from a table where certain fields contain certain information and just select the entire row? If so, I think you are getting too complicated. You need to identify the object to test, in this case a datarow, followed by the collection, in this case all the rows of the datatable, perform your criteria on the row just as if you were doing a foreach statement and had access to the variable you defined after the from, and then select the variable you defined.

Like so

DataTable dt = new DataTable();
DataRow row;
 
dt.Columns.Add(new DataColumn("id",typeof(int)));
 
row = dt.NewRow();
row["id"] = 1;
dt.Rows.Add(row);
 
row = dt.NewRow();
row["id"] = 2;
dt.Rows.Add(row);
 
row = dt.NewRow();
row["id"] = 3;
dt.Rows.Add(row);
 
MessageBox.Show((from DataRow r in dt.Rows where r["id"].ToString() == "1" select r).Count<DataRow>().ToString());

                                              
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by: DhaestPosted on 2009-09-16 at 05:19:14ID: 25344734

The only solution I saw for this (even no solution with linq), is to loop over all the rows and all the columns.

 

by: FLOG51Posted on 2009-09-16 at 05:31:25ID: 25344843

Hi robkolsky

I must be missing something I am very new to C#, I am not sure why you are providing and id to the Columns, when they already have field headers in the datatable.

I have already built all of this code in normal switch statement but it is very long winded as well as providing difficulty in separating the row data; and LINQ promises to simplify by query directly to object.

I have a datatable with a field called "Status" and in that field I will get 3 variables "PENDING", "SUCCESS" or "FAIL". I am attempting to use LINQ to get all the row data where status = PENDING.

FLOG51



 

by: FLOG51Posted on 2009-09-16 at 05:33:10ID: 25344859

Hi daryal

Yes that looks more like what I have been searching for, how do I output that to a Console.

FLOG51

 

by: DhaestPosted on 2009-09-16 at 05:34:00ID: 25344864

To resume, do you want to search records where in a specific field is a value or search records where a value in one of the columns of the datatable ?

 

by: FLOG51Posted on 2009-09-16 at 05:49:35ID: 25344994

Hi I want to search by a value in one of the columns i.e. I have 10 columns in the datatable with field headers:

Receipt, ID, Ref, GenRef, PayDate, Amount, PayRef, PayMeth, Status, NextDate

I want to retrieve all the row data where the value of Status = PENDING.

In MySQL query I would write "SELECT * FROM `myTable` WHERE `status` = 'PENDING'

 

by: daryalPosted on 2009-09-16 at 05:53:35ID: 25345027

Use the query I have provided,
That does what you need.

 

by: DhaestPosted on 2009-09-16 at 05:58:46ID: 25345068

I agree with daryal, that query should do the trick

To output the result to a console
http://www.java2s.com/Code/CSharp/LINQ/Useforeachlooptodealwiththeresultfromlinq.htm

 

by: robkolskyPosted on 2009-09-16 at 05:59:17ID: 25345074

Id was just a field name i used as I created my own sample field. Daryal, it looks like you are assuming a Typed data set. If the dataset isn't typed the query would look like

var allTableInfo = from o in dt
where o["Status"].ToString() == "PENDING"
select o;

 

by: FLOG51Posted on 2009-09-16 at 06:28:36ID: 25345336

Hi robkolsky

that was the clue I needed. Select o; crashed until I applied your ["Field"].ToString() logic.

The code below outputs a line foreach i with all row data that meets the PENDING criteria.

public void testLINQ(DataTable dt)
  {        
     IEnumerable<DataRow> seq1 = dt.AsEnumerable();
 
     var allTableInfo = from tableInfo in seq1
                        where
                        tableInfo["Status"].ToString() == "PENDING"
select 
tableInfo["Receipt"].ToString() +", "+ tableInfo["ID"].ToString() + ", " + tableInfo["Ref"].ToString() +", "+ tableInfo["GenRef"].ToString() + ", " + tableInfo["PayDate"].ToString() + ", " + tableInfo["Amount"].ToString() +", "+ tableInfo["PayRef"].ToString() + ", " + tableInfo["PayMeth"].ToString() +", "+ tableInfo["Status"].ToString() +", "+ tableInfo["NextDate"].ToString();
 
            foreach (string i in allTableInfo)
                Console.WriteLine(i);                
  }

                                              
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by: daryalPosted on 2009-09-16 at 06:38:55ID: 25345439

Hello,
By the way, thanks for sharing your code.

20120131-EE-VQP-002

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