/// <summary>
/// Gets an Expression that gets the value of a POCO field or property.
/// </summary>
private Expression GetExpressionToGetValueFromPoco(ParameterExpression poco, PocoColumn column)
{
// Start by assuming the database wants the same type that the property is and that we'll just be getting the value from the property:
// poco.SomeFieldOrProp
Expression getValueFromPoco = Expression.MakeMemberAccess(poco, column.MemberInfo);
if (column.MemberInfoType == column.ColumnType)
{
return(getValueFromPoco);
}
// See if there is a converter available for between the two types
Delegate converter = _typeConverter.GetToDbConverter(column.MemberInfoType, column.ColumnType);
if (converter == null)
{
// No converter available, at least try a cast:
// (TColumn) poco.SomeFieldOrProp
return(Expression.Convert(getValueFromPoco, column.ColumnType));
}
// Invoke the converter:
// converter(poco.SomeFieldOrProp)
return(Expression.Call(converter.Target == null ? null : Expression.Constant(converter.Target), converter.Method, getValueFromPoco));
}
/// <summary>
/// Creates a Func that collects all the values from a POCO (of type T) into an object[], with the values being in the array in the
/// same order as the POCO's PocoData.Columns collection.
/// </summary>
private Func <T, object[]> CreateValueCollector <T>(bool primaryKeyValuesOnly)
{
PocoData pocoData = _pocoDataFactory.GetPocoData <T>();
// Create list to hold the method body and our input parameter, the POCO of type T
var methodBodyExpressions = new List <Expression>();
ParameterExpression poco = Expression.Parameter(pocoData.PocoType, "poco");
// Figure out which collection of columns to use
IList <PocoColumn> columns = primaryKeyValuesOnly == false
? pocoData.Columns
: pocoData.GetPrimaryKeyColumns();
// Create a variable to hold our return value, and initialize as an object[] of correct size
var values = Expression.Variable(typeof(object[]), "values");
methodBodyExpressions.Add(
// object[] values = new object[... number of columns on POCO ...];
Expression.Assign(values, Expression.NewArrayBounds(ObjectType, Expression.Constant(columns.Count, IntType))));
for (var idx = 0; idx < columns.Count; idx++)
{
PocoColumn column = columns[idx];
// Figure out how to get the
Expression getValueFromPoco = GetExpressionToGetValueFromPoco(poco, column);
// values[columnIndex] = (object) ... getValueFromPoco ...
methodBodyExpressions.Add(
Expression.Assign(Expression.ArrayAccess(values, Expression.Constant(idx, IntType)),
Expression.Convert(getValueFromPoco, ObjectType))
);
}
// Return our values array
methodBodyExpressions.Add(values);
// Construct the method body, then create a compiled Func for the method
var methodBody = Expression.Block(new[] { values }, methodBodyExpressions);
return(Expression.Lambda <Func <T, object[]> >(methodBody, poco).Compile());
}
