Dynamic PIVOT using C# Linq

Question

I am trying to use following code to create the PIVOT but its not working.

It\'s giving me compile time error. I don\'t know linq so unable to use it.

Please

Answer 1

Here is the code with the compilation errors corrected:

DataTable Pivot(DataTable dt, DataColumn pivotColumn, DataColumn pivotValue) {
    // find primary key columns 
    //(i.e. everything but pivot column and pivot value)
    DataTable temp = dt.Copy();
    temp.Columns.Remove( pivotColumn.ColumnName );
    temp.Columns.Remove( pivotValue.ColumnName );
    string[] pkColumnNames = temp.Columns.Cast<DataColumn>()
        .Select( c => c.ColumnName )
        .ToArray();

    // prep results table
    DataTable result = temp.DefaultView.ToTable(true, pkColumnNames).Copy();
    result.PrimaryKey = result.Columns.Cast<DataColumn>().ToArray();
    dt.AsEnumerable()
        .Select(r => r[pivotColumn.ColumnName].ToString())
        .Distinct().ToList()
        .ForEach (c => result.Columns.Add(c, pivotColumn.DataType));

    // load it
    foreach( DataRow row in dt.Rows ) {
        // find row to update
        DataRow aggRow = result.Rows.Find(
            pkColumnNames
                .Select( c => row[c] )
                .ToArray() );
        // the aggregate used here is LATEST 
        // adjust the next line if you want (SUM, MAX, etc...)
        aggRow[row[pivotColumn.ColumnName].ToString()] = row[pivotValue.ColumnName];
    }

    return result;
}

I changed Cast(<DataColumn>) to Cast<DataColumn>() in two locations and got rid of the semicolon in the middle of a lambda expression. The second part of your question is a little trickier. You may want to ask it as its own question.

Answer 2

Good one., but you might want to replace the below line

 .ForEach (c => result.Columns.Add(c, pivotColumn.DataType));

with this (change pivotColumn to pivotValue)

 .ForEach (c => result.Columns.Add(c, pivotValue.DataType));

Works perfectly for my requirement.