Linq to DataSets

Distinct

• removes duplicate rows from a sequence of object
• public static IEnumerable<TSource> Distinct<TSource>( this IEnumerable<TSource> source )
  
• dataRow.Field<int>(0)
• IEnumerable<DataRow> distinct = dt.AsEnumerable().Distinct(DataRowComparer.Default)

Except

• Produces the set of DataRow object difference of two sequences
  

Intersect

SequenceEqual

•  compares two sequence of DataRow objects to determine whether they are equal

System.Data.DataRowExtensions

• Defines the extension methods to the DataRow class. This is a static class.
  
• Field<T>
• where c.Field<int>("ID") == s.Field<int>("ID")
• Provides strongly-typed access to each of the column values in the DataRow.
  
• public static T Field<T>( this DataRow row, string columnName[, DataRowVersion version] )
• row.AcceptChanges()
• called to make DataRow object to accept the current value for each DataColumn object within it as the original version
• SetField<T>
• Sets a new value for the specified column in the DataRow
  

DataTable Operators (System.Data.DataTableExtensions)

•  .AsEnumerable()
• Returns an IEnumerable<T> object, where the generic parameter T is DataRow. This object can be used in a LINQ expression or method query.
  
• .CopyToDataTable<DataRow>
  
• Returns a DataTable that contains copies of the DataRow objects, given an input IEnumerable<T> object.
  
• System.Data.LoadOption
  
• A LoadOption enumeration that specifies the DataTable load options.
  
• OverwriteChanges: the incoming values for this row will be written to both the current value and the original value versions of the data for each column.
  
• PreserveChanges: the incoming values for this row will be written to the original value version of each column. The current version of the data in each column will not be changed. [This] is the default.
  
• Upsert: The incoming values for this row will be written to the current version of each column. The original version of each column's data will not be changed.
• DataRow.HasVersion
• to determine if there is an original version
• dt.AcceptChanges()

System.Data.SqlClient

• dataSet.Tables["Students"]
• dataRow.Field<string>("Name")
• or dataRow.Name in typed DataSet objects
• studsDS.Students.AddStudentRow(1, "George");
• studsDS.Students.where(student => student.ID == 7).Single().Name;
• 
  string connString = @"Data Source = .\SQLEXPRESS; InitialCatalog = Northwing; IntegrationSecurity = SSPI";
  SqlDataAdapter sda = new SqlDataAdapter("Select ... ", connString);
  DataSet ds = new DataSet();
  sda.Fill(ds, "Students");
  ds.Tables("Students").AsEnumerable()
• Where
• Distinct