/// <summary>
/// Execute the command and return the first column of the first row of the resultset
/// (if present), or null if no resultset was returned.
/// </summary>
/// <returns>The first column of the first row of the first resultset from the query</returns>
public override object ExecuteScalar()
{
InitializeForReader();
int x = 0;
object ret = null;
SqliteType typ = new SqliteType();
SqliteStatement stmt;
// We step through every statement in the command, but only grab the first row of the first resultset.
// We keep going even after obtaining it.
for (;;)
{
stmt = GetStatement(x);
x++;
if (stmt == null)
{
break;
}
if (_cnn._sql.Step(stmt) == true && ret == null)
{
ret = _cnn._sql.GetValue(stmt, 0, typ);
}
_cnn._sql.Reset(stmt);
}
return(ret);
}
/// <summary>
/// Retrieves the SqliteType for a given column, and caches it to avoid repetetive interop calls.
/// </summary>
/// <param name="i">The index of the column to retrieve</param>
/// <returns>A SqliteType structure</returns>
private SqliteType GetSqliteType(int i)
{
SqliteType typ;
// Initialize the field types array if not already initialized
if (_fieldTypeArray == null)
{
_fieldTypeArray = new SqliteType[VisibleFieldCount];
}
// Initialize this column's field type instance
if (_fieldTypeArray[i] == null)
{
_fieldTypeArray[i] = new SqliteType();
}
typ = _fieldTypeArray[i];
// If not initialized, then fetch the declared column datatype and attempt to convert it
// to a known DbType.
if (typ.Affinity == TypeAffinity.Uninitialized)
{
typ.Type = SqliteConvert.TypeNameToDbType(_activeStatement._sql.ColumnType(_activeStatement, i, out typ.Affinity));
}
else
{
typ.Affinity = _activeStatement._sql.ColumnAffinity(_activeStatement, i);
}
return(typ);
}
/// <summary>
/// Determines the data type of a column in a statement
/// </summary>
/// <param name="stmt">The statement to retrieve information for</param>
/// <param name="i">The column to retrieve type information on</param>
/// <returns>Returns a SqliteType struct</returns>
internal static SqliteType ColumnToType(SqliteStatement stmt, int i)
{
SqliteType typ = new SqliteType();
typ.Type = TypeNameToDbType(stmt._sql.ColumnType(stmt, i, out typ.Affinity));
return(typ);
}
/// <summary>
/// Converts a SqliteType to a .NET Type object
/// </summary>
/// <param name="t">The SqliteType to convert</param>
/// <returns>Returns a .NET Type object</returns>
internal static Type SqliteTypeToType(SqliteType t)
{
if (t.Type != DbType.Object)
{
return(SqliteConvert.DbTypeToType(t.Type));
}
return(_typeaffinities[(int)t.Affinity]);
}
/// <summary>
/// Retrieves the column as an object corresponding to the underlying datatype of the column
/// </summary>
/// <param name="i">The index of the column to retrieve</param>
/// <returns>object</returns>
public override object GetValue(int i)
{
CheckClosed();
#if MONO_SUPPORT_KEYREADER
if (i >= VisibleFieldCount && _keyInfo != null)
{
return(_keyInfo.GetValue(i - VisibleFieldCount));
}
#endif
SqliteType typ = GetSqliteType(i);
typ.Affinity = _activeStatement._sql.ColumnAffinity(_activeStatement, i);
return(_activeStatement._sql.GetValue(_activeStatement, i, typ));
}
/// <summary>
/// Helper function to retrieve a column of data from an active statement.
/// </summary>
/// <param name="stmt">The statement being step()'d through</param>
/// <param name="index">The column index to retrieve</param>
/// <param name="typ">The type of data contained in the column. If Uninitialized, this function will retrieve the datatype information.</param>
/// <returns>Returns the data in the column</returns>
internal override object GetValue(SqliteStatement stmt, int index, SqliteType typ)
{
if (typ.Affinity == 0)
{
typ = SqliteConvert.ColumnToType(stmt, index);
}
if (IsNull(stmt, index))
{
return(DBNull.Value);
}
Type t = SqliteConvert.SqliteTypeToType(typ);
switch (TypeToAffinity(t))
{
case TypeAffinity.Blob:
if (typ.Type == DbType.Guid && typ.Affinity == TypeAffinity.Text)
{
return(new Guid(GetText(stmt, index)));
}
int n = (int)GetBytes(stmt, index, 0, null, 0, 0);
byte[] b = new byte[n];
GetBytes(stmt, index, 0, b, 0, n);
if (typ.Type == DbType.Guid && n == 16)
{
return(new Guid(b));
}
return(b);
case TypeAffinity.DateTime:
return(GetDateTime(stmt, index));
case TypeAffinity.Double:
return(Convert.ChangeType(GetDouble(stmt, index), t, null));
case TypeAffinity.Int64:
return(Convert.ChangeType(GetInt64(stmt, index), t, null));
default:
return(GetText(stmt, index));
}
}
/// <summary>
/// Retrieves the name of the back-end datatype of the column
/// </summary>
/// <param name="i">The index of the column to retrieve</param>
/// <returns>string</returns>
public override string GetDataTypeName(int i)
{
CheckClosed();
#if MONO_SUPPORT_KEYREADER
if (i >= VisibleFieldCount && _keyInfo != null)
{
return(_keyInfo.GetDataTypeName(i - VisibleFieldCount));
}
#endif
SqliteType typ = GetSqliteType(i);
if (typ.Type == DbType.Object)
{
return(SqliteConvert.SqliteTypeToType(typ).Name);
}
return(_activeStatement._sql.ColumnType(_activeStatement, i, out typ.Affinity));
}
internal abstract object GetValue(SqliteStatement stmt, int index, SqliteType typ);
/// <summary>
/// Retrieves the SqliteType for a given column, and caches it to avoid repetetive interop calls.
/// </summary>
/// <param name="i">The index of the column to retrieve</param>
/// <returns>A SqliteType structure</returns>
private SqliteType GetSqliteType(int i)
{
SqliteType typ;
// Initialize the field types array if not already initialized
if (_fieldTypeArray == null) _fieldTypeArray = new SqliteType[VisibleFieldCount];
// Initialize this column's field type instance
if (_fieldTypeArray[i] == null) _fieldTypeArray[i] = new SqliteType();
typ = _fieldTypeArray[i];
// If not initialized, then fetch the declared column datatype and attempt to convert it
// to a known DbType.
if (typ.Affinity == TypeAffinity.Uninitialized)
typ.Type = SqliteConvert.TypeNameToDbType(_activeStatement._sql.ColumnType(_activeStatement, i, out typ.Affinity));
else
typ.Affinity = _activeStatement._sql.ColumnAffinity(_activeStatement, i);
return typ;
}
/// <summary>
/// Execute the command and return the first column of the first row of the resultset
/// (if present), or null if no resultset was returned.
/// </summary>
/// <returns>The first column of the first row of the first resultset from the query</returns>
public override object ExecuteScalar()
{
InitializeForReader();
int x = 0;
object ret = null;
SqliteType typ = new SqliteType();
SqliteStatement stmt;
// We step through every statement in the command, but only grab the first row of the first resultset.
// We keep going even after obtaining it.
for (;;)
{
stmt = GetStatement(x);
x++;
if (stmt == null) break;
if (_cnn._sql.Step(stmt) == true && ret == null)
{
ret = _cnn._sql.GetValue(stmt, 0, typ);
}
_cnn._sql.Reset(stmt);
}
return ret;
}
internal abstract object GetValue(SqliteStatement stmt, int index, SqliteType typ);
/// <summary>
/// Converts a SqliteType to a .NET Type object
/// </summary>
/// <param name="t">The SqliteType to convert</param>
/// <returns>Returns a .NET Type object</returns>
internal static Type SqliteTypeToType(SqliteType t)
{
if (t.Type != DbType.Object)
return SqliteConvert.DbTypeToType(t.Type);
return _typeaffinities[(int)t.Affinity];
}
/// <summary>
/// Determines the data type of a column in a statement
/// </summary>
/// <param name="stmt">The statement to retrieve information for</param>
/// <param name="i">The column to retrieve type information on</param>
/// <returns>Returns a SqliteType struct</returns>
internal static SqliteType ColumnToType(SqliteStatement stmt, int i)
{
SqliteType typ = new SqliteType ();
typ.Type = TypeNameToDbType(stmt._sql.ColumnType(stmt, i, out typ.Affinity));
return typ;
}