/// <summary>
/// Checks whether the projection references the projector's parameter.
/// </summary>
/// <param name="expression">Projector.</param>
public void Validate(Expression expression)
{
var projector = (LambdaExpression)expression;
var paramSeeker = new ParameterSeeker();
if (!paramSeeker.Exists(projector.Body, projector.Parameters[0]))
{
throw new InvalidProjectionException("The projection does not hold any reference to the projector's parameter.", projector.Body);
}
}
protected override Expression VisitColumn(ColumnExpression c)
{
string columnName = string.Empty;
Type columnDataType = null;
bool isNullable = false;
Expression columnMapper = c.ColumnMapper;
if (_memberInScope != null)
{
columnName = _memberInScope.Name;
columnDataType = ((PropertyInfo)_memberInScope).PropertyType;
_memberInScope = null;
}
if (columnMapper is ConstantExpression constantExp && constantExp.Value is ColumnSettings columnSettings)
{
columnMapper = ((LambdaExpression)columnSettings.Mapper).Body;
columnName = !string.IsNullOrEmpty(columnSettings.ColumnName) ? columnSettings.ColumnName : columnName;
columnDataType = columnSettings.ColumnDataType;
}
if (string.IsNullOrEmpty(columnName))
{
throw new InvalidOperationException("Can't find/infer the column's name. Review your projection and ensure you either implicit or explicitily you set the column's name.");
}
if (columnDataType == typeof(string))
{
isNullable = true;
}
else
{
Type nullableType = Nullable.GetUnderlyingType(columnDataType);
if (nullableType != null)
{
columnDataType = nullableType;
isNullable = true;
}
}
if (!columnDataType.IsBuiltInType())
{
throw new InvalidColumnDataTypeException($"The data type for the column \"{columnName}\" is invalid: {columnDataType.ToString()}.");
}
LambdaExpression le = null;
bool isMapperExprParameterless = !_parameterSeeker.Exists(columnMapper, _projectorParameter);
if (isMapperExprParameterless)
{
le = Expression.Lambda(columnMapper);
}
else
{
le = Expression.Lambda(columnMapper, _projectorParameter);
}
var column = new Column()
{
Name = columnName,
DataType = columnDataType,
IsNullable = isNullable,
Mapper = le.Compile(),
IsMapperParameterless = isMapperExprParameterless
};
_columns.Add(column);
return(c);
}