DataTable Relational Operators in C# - INTERSECT Method, DISTINCT helper method & an apology (2009-11-03)
If anybody can come up with a faster solution for Distinct it would be most appreciated.
public static DataTable Intersect(DataTable First, DataTable Second)
{
//Get reference to Columns in First
DataColumn[] firstcolumns = new DataColumn[First.Columns.Count];
for(int i = 0; i < firstcolumns.Length; i++)
{
firstcolumns[i] = First.Columns[i];
}
//Get reference to Columns in Second
DataColumn[] secondcolumns = new DataColumn[Second.Columns.Count];
for(int i = 0; i < secondcolumns.Length; i++)
{
secondcolumns[i] = Second.Columns[i];
}
//JOIN ON all columns
DataTable table = SQLOps.Join(First, Second, firstcolumns, secondcolumns);
table.TableName = "Intersect";
return table;
}
private static bool RowEqual(object[] Values, object[] OtherValues)
{
if(Values == null)
return false;
for(int i = 0; i < Values.Length; i++)
{
if(!Values[i].Equals(OtherValues[i]))
return false;
}
return true;
}
public static DataTable Distinct(DataTable Table, DataColumn[] Columns)
{
//Empty table
DataTable table = new DataTable("Distinct");
//Sort variable
string sort = string.Empty;
//Add Columns & Build Sort expression
for(int i = 0; i < Columns.Length; i++)
{
table.Columns.Add(Columns[i].ColumnName,Columns[i].DataType);
sort += Columns[i].ColumnName + ",";
}
//Select all rows and sort
DataRow[] sortedrows = Table.Select(string.Empty,sort.Substring(0,sort.Length-1));
object[] currentrow = null;
object[] previousrow = null;
table.BeginLoadData();
foreach(DataRow row in sortedrows)
{
//Current row
currentrow = new object[Columns.Length];
for(int i = 0; i < Columns.Length; i++)
{
currentrow[i] = row[Columns[i].ColumnName];
}
//Match Current row to previous row
if(!SQLOps.RowEqual(previousrow, currentrow))
table.LoadDataRow(currentrow,true);
//Previous row
previousrow = new object[Columns.Length];
for(int i = 0; i < Columns.Length; i++)
{
previousrow[i] = row[Columns[i].ColumnName];
}
}
table.EndLoadData();
return table;
}
public static DataTable Distinct(DataTable Table, DataColumn Column)
{
return Distinct(Table, new DataColumn[]{Column});
}
public static DataTable Distinct(DataTable Table, string Column)
{
return Distinct(Table, Table.Columns[Column]);
}
public static DataTable Distinct(DataTable Table, params string[] Columns)
{
DataColumn[] columns = new DataColumn[Columns.Length];
for(int i = 0; i < Columns.Length; i++)
{
columns[i] = Table.Columns[Columns[i]];
}
return Distinct(Table, columns);
}
public static DataTable Distinct(DataTable Table)
{
DataColumn[] columns = new DataColumn[Table.Columns.Count];
for(int i = 0; i < Table.Columns.Count; i++)
{
columns[i] = Table.Columns[i];
}
return Distinct(Table, columns);
}
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