Pivot table using LINQ

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Hey everyone. I have such a table:

------------
name | value
------------
n1   | v1
n2   | v2
n3   | v3
------------

What is needed to be done is this:

------------
n1 | n2 | n3
------------
v1 | v2 | v3
------------

The thing is, table is a real life MSSQL table sitting in a database. Currently I am pivoting it using T-SQL Pivot, but need to do it with LINQ. Apart from that, new table have to be sortable as a regular table.
So, is that even possible? If it is - is there anyone, who knows how to do it? BTW, everything is dynamic here, and dynamic sql is used for T-SQL, columns are dynamic, etc.

What I have tried:

I've read probably everything on the net how to pivot tables, but nothing worked so far.

Posted 7-Mar-20 7:12am

csrss

Updated 8-Mar-20 10:52am

Maciej Los

v3

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Maciej Los 7-Mar-20 14:51pm

There's no data on which data can be pivoted (group by).
:(

2 solutions

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Maciej Los · Answer 1 · 2020-03-08T10:53:00

Take a look at below example (created in LinqPad):

C#

void Main()
{
	DataTable srcdt = GetInitialData();
	List<KeyValuePair<string, string>> data = srcdt.AsEnumerable()
		.Select(x=>new KeyValuePair<string, string>(x[0].ToString(), x[1].ToString()))
		.ToList();
	
	DataTable dstdt = new DataTable();
	List<string> cols = data.Select(x=> x.Key).Distinct().ToList();
	dstdt.Columns.AddRange(cols.Select(x=>new DataColumn(x, typeof(string))).ToArray());

	if(cols.Count != srcdt.Rows.Count)
		Console.WriteLine("The number of columns does not equal to no. of rows in source table!");
	else
	{
		DataRow dr = dstdt.NewRow();
		foreach(KeyValuePair<string, string> kvp in data)
		{
			dr[kvp.Key] = kvp.Value;
		}
		dstdt.Rows.Add(dr);
	}
	dstdt.Dump();
}

// Define other methods and classes here
DataTable GetInitialData()
{
	DataTable dt = new DataTable();
	dt.Columns.AddRange(new DataColumn[]
		{
			new DataColumn("name", typeof(string)),
			new DataColumn("value", typeof(string))
		});
	dt.Rows.Add(new object[]{"n1", "v1"});
	dt.Rows.Add(new object[]{"n2", "v2"});
	dt.Rows.Add(new object[]{"n3", "v3"});

	return dt;
}

Note: If there would be non-unique data, you'll be in trouble ;)

Gerry Schmitz · Answer 2 · 2020-03-07T09:25:00

Solution 1

Don't know why you "need" to use LINQ (you could use it for "some" parts).

Create a <name,value> dictionary and "sum" the values by adding to and updating the dictionary.

At "report" time, print the "keys" as headings, and the "values" as column values.

(With LINQ, you groupby on name with a sum on value, then foreach 2 times for printing, assuming its now ordered)

For "report" / printing substitute array, data row, etc. based on context.

Posted 7-Mar-20 9:25am

Gerry Schmitz

Updated 7-Mar-20 9:33am

v2

Comments

csrss 7-Mar-20 15:30pm

There is no numeric data - all rows and columns consist of string values. No, I cannot do it like you say - pivoted table is applied to a bigger query so the result table is returned which has all possibilities of sorting and filtering data data.

[no name] 7-Mar-20 15:35pm

It works for "strings", assuming they're unique. If the strings are NOT unique, then PIVOTING WON'T WORK. The rest of your "reason" makes no sense.

csrss 7-Mar-20 15:39pm

You see, I have already tried such solution as yours, but unfortunately it does not work.

Pivot table using LINQ

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Pivot table using LINQ

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