// only used with ADO writers
// TODO this method can be greatly simplified
protected internal DataSet CreateDataSetFromCursorColumns()
{
DataSet retval = null;
List <TableDef> tables = GetTableInfoFromCursorColumns();
// we have now collected all table info,
// we can create a dataset
DataTable dt = null;
DataTable primaryTable = null; //hack
for (int i = 0; i < tables.Count; i++)
{
if (retval == null)
{
retval = new DataSet(this._dataSourceName);
}
TableDef td = tables[i];
try
{
dt = retval.Tables.Add(td.Name);
}
catch (DuplicateNameException)
{
// TODO deal with this
// It is a rare exception, but possible. Commence connection names are case-sensitive.
// In that case this exception is not thrown, but data can still end up in the wrong datatable (or more likely fail).
// we should probably include some pre-check and throw something more meaningful
throw; // for now just rethrow to be safe
}
// define columns
DataColumn dc = null;
// we need to set some general fields
if (td.Primary) // primary table columns
{
dc = dt.Columns.Add("id", typeof(Int32)); // not auto-incremented!
dc.AllowDBNull = false;
// hack for setting relations later on.
primaryTable = dt; // capture that this is our primary table so we can set relationships later on
dt.ExtendedProperties.Add("IsPrimaryTable", true);
}
else // related table columns
{
// create a primary key that autoincrements
dc = dt.Columns.Add("id", typeof(Int32));
dc.AllowDBNull = false;
dc.AutoIncrement = true;
// create a foreign key field to reference the connected item
dc = dt.Columns.Add("fkid", typeof(Int32));
dc.AllowDBNull = false; // cannot be null
}
// now process Commence fields
// rest of related columns
for (int j = 0; j < td.ColumnDefinitions.Count; j++)
{
try
{
dc = dt.Columns.Add(td.ColumnDefinitions[j].FieldName);
}
catch (DuplicateNameException)
{
// appending some number would decouple the fieldname in the dataset
// from the fieldname in the Commence columnset.
// for now just rethrow
throw;
}
// set column properties
dc.DataType = td.ColumnDefinitions[j].CommenceFieldDefinition.Type.GetTypeForCommenceField();
dc.AllowDBNull = true; // this is default, but setting it explicitly makes it more clear.
}
}
// we would like to set relationships as well.
// as it is, we don't know what our 'primary' table is at this point in the code
// all we know it is the only table without a fkid field, but that's a little awkward to check.
// we hack that by having a 'mock' primary table variable.
List <DataRelation> relations = new List <DataRelation>();
foreach (DataTable d in retval.Tables)
{
if (!d.Equals(primaryTable))
{
DataRelation r = new DataRelation("rel_" + d.TableName,
primaryTable.TableName,
d.TableName,
new string[] { "id" },
new string[] { "fkid" },
true); // setting nested to true allows for nested XML exports
relations.Add(r);
}
}
// add the relations to the dataset
// tricky snag found on https://msdn.microsoft.com/en-us/library/2z22c2sz.aspx
// "Any DataRelation object created by using this constructor must be added to the collection
// with the AddRange method inside of a BeginInit and EndInit block.
if (relations.Any())
{
retval.BeginInit();
retval.Relations.AddRange(relations.ToArray());
retval.EndInit();
}
return(retval);
}