DataTable schemaTable =
oledbConnection.GetOleDbSchemaTable(OleDbSchemaGuid.Foreign_Keys,
new object[] {null, null, "OneTableName"});
или
DataTable schemaTable =
oledbConnection.GetOleDbSchemaTable(OleDbSchemaGuid.Foreign_Keys,
new object[] {null, null, "OneTableName", null, null, "OtherTableName"});