/// <summary>
/// Creates a <see cref="ColumnDefinition"/> object representing the column passed in by <paramref name="columnList"/>.
/// </summary>
/// <param name="database">The database.</param>
/// <param name="tableName">Name of the table.</param>
/// <param name="columnList">The <see cref="JET_COLUMNLIST"/> object that represents the row in
/// the temptable for this particular column.</param>
/// <returns>
/// A <see cref="ColumnDefinition"/> object based on the current row in the temptable
/// represented by <paramref name="columnList"/>.
/// </returns>
internal static ColumnDefinition Load(IsamDatabase database, string tableName, JET_COLUMNLIST columnList)
{
lock (database.IsamSession)
{
using (IsamTransaction trx = new IsamTransaction(database.IsamSession))
{
// load info for the column
ColumnDefinition columnDefinition = new ColumnDefinition();
JET_SESID sesid = database.IsamSession.Sesid;
// As of Sep 2015, JetGetColumnInfoW is only called for Win8+. Even though Unicode should have
// worked in Win7, it wasn't reliable until Win8.
Encoding encodingOfTextColumns = EsentVersion.SupportsWindows8Features ? Encoding.Unicode : LibraryHelpers.EncodingASCII;
string columnName = Api.RetrieveColumnAsString(
database.IsamSession.Sesid,
columnList.tableid,
columnList.columnidcolumnname,
encodingOfTextColumns);
JET_COLUMNBASE columnbase;
Api.JetGetColumnInfo(database.IsamSession.Sesid, database.Dbid, tableName, columnName, out columnbase);
columnDefinition.columnid = new Columnid(columnbase);
columnDefinition.name = columnDefinition.columnid.Name;
columnDefinition.type = columnDefinition.columnid.Type;
ColumndefGrbit grbitColumn = (ColumndefGrbit)Api.RetrieveColumnAsUInt32(sesid, columnList.tableid, columnList.columnidgrbit).GetValueOrDefault();
columnDefinition.flags = ColumnFlagsFromGrbits(grbitColumn);
columnDefinition.maxLength = Api.RetrieveColumnAsInt32(sesid, columnList.tableid, columnList.columnidcbMax).GetValueOrDefault();
columnDefinition.IsAscii = columnbase.cp == JET_CP.ASCII;
byte[] defaultValueBytes = Api.RetrieveColumn(sesid, columnList.tableid, columnList.columnidDefault);
Columnid isamColumnid = columnDefinition.columnid;
columnDefinition.defaultValue = Converter.ObjectFromBytes(
isamColumnid.Coltyp,
columnDefinition.IsAscii,
defaultValueBytes);
columnDefinition.ReadOnly = true;
return(columnDefinition);
}
}
}
/// <summary>
/// Retrieves the column.
/// </summary>
/// <param name="columnid">The columnid.</param>
/// <param name="coltyp">The coltyp.</param>
/// <param name="isAscii">Whether a textual column is Ascii.</param>
/// <param name="index">The index.</param>
/// <returns>The value stored within.</returns>
/// <remarks>
/// Itags start at 1, so we add 1 to the index
/// </remarks>
private object RetrieveColumn(JET_COLUMNID columnid, JET_coltyp coltyp, bool isAscii, int index)
{
lock (this.isamSession)
{
this.cursor.CheckDisposed();
if ((this.grbit & RetrieveColumnGrbit.RetrieveCopy) == 0)
{
this.cursor.CheckRecord();
}
JET_RETINFO retinfo = new JET_RETINFO();
retinfo.ibLongValue = 0;
retinfo.itagSequence = index + 1;
byte[] bytes = Api.RetrieveColumn(this.isamSession.Sesid, this.tableid, columnid, this.grbit, retinfo);
object obj = Converter.ObjectFromBytes(coltyp, isAscii, bytes);
return(obj);
}
}
/// <summary>
/// Creates a <see cref="ColumnDefinition"/> object representing the column passed in by <paramref name="columnBase"/>.
/// </summary>
/// <param name="database">The database.</param>
/// <param name="tableName">Name of the table.</param>
/// <param name="columnBase">The <see cref="JET_COLUMNBASE"/> object that represents this particular column.</param>
/// <returns>
/// A <see cref="ColumnDefinition"/> object based on the <paramref name="columnBase"/> object.
/// </returns>
internal static ColumnDefinition Load(IsamDatabase database, string tableName, JET_COLUMNBASE columnBase)
{
lock (database.IsamSession)
{
using (IsamTransaction trx = new IsamTransaction(database.IsamSession))
{
JET_SESID sesid = database.IsamSession.Sesid;
// load info for the column
ColumnDefinition columnDefinition = new ColumnDefinition();
columnDefinition.columnid = new Columnid(columnBase);
columnDefinition.name = columnDefinition.columnid.Name;
columnDefinition.type = columnDefinition.columnid.Type;
columnDefinition.flags = ColumnFlagsFromGrbits(columnBase.grbit);
columnDefinition.maxLength = (int)columnBase.cbMax;
columnDefinition.IsAscii = columnBase.cp == JET_CP.ASCII;
// there is currently no efficient means to retrieve the
// default value of a specific column from JET. so, we are
// going to reach into the catalog and fetch it directly
JET_TABLEID tableidCatalog;
Api.JetOpenTable(
sesid,
database.Dbid,
"MSysObjects",
null,
0,
OpenTableGrbit.ReadOnly,
out tableidCatalog);
Api.JetSetCurrentIndex(sesid, tableidCatalog, "RootObjects");
Api.MakeKey(sesid, tableidCatalog, true, MakeKeyGrbit.NewKey);
Api.MakeKey(
sesid,
tableidCatalog,
Converter.BytesFromObject(JET_coltyp.Text, true, columnBase.szBaseTableName),
MakeKeyGrbit.None);
Api.JetSeek(sesid, tableidCatalog, SeekGrbit.SeekEQ);
JET_COLUMNBASE columnbaseCatalog;
Api.JetGetTableColumnInfo(sesid, tableidCatalog, "ObjidTable", out columnbaseCatalog);
uint objidTable = Api.RetrieveColumnAsUInt32(sesid, tableidCatalog, columnbaseCatalog.columnid).GetValueOrDefault();
Api.JetSetCurrentIndex(sesid, tableidCatalog, "Name");
Api.MakeKey(sesid, tableidCatalog, objidTable, MakeKeyGrbit.NewKey);
Api.MakeKey(sesid, tableidCatalog, (short)2, MakeKeyGrbit.None);
Api.MakeKey(sesid, tableidCatalog, columnBase.szBaseColumnName, Encoding.ASCII, MakeKeyGrbit.None);
Api.JetSeek(sesid, tableidCatalog, SeekGrbit.SeekEQ);
Api.JetGetTableColumnInfo(sesid, tableidCatalog, "DefaultValue", out columnbaseCatalog);
byte[] defaultValueBytes = Api.RetrieveColumn(sesid, tableidCatalog, columnbaseCatalog.columnid);
Columnid isamColumnid = columnDefinition.columnid;
columnDefinition.defaultValue = Converter.ObjectFromBytes(
isamColumnid.Coltyp,
columnDefinition.IsAscii,
defaultValueBytes);
columnDefinition.ReadOnly = true;
return(columnDefinition);
}
}
}