private Func <String, TRecord> CreateLineParser()
{
ParameterExpression lineExpression = Expression.Parameter(typeof(String), "line");
ParameterExpression returnExpression = Expression.Variable(typeof(TRecord), "ret");
ParameterExpression stringsExpression = Expression.Variable(typeof(String[]), "strings");
List <Expression> expressions =
new List <Expression> {
Expression.Assign(returnExpression, Expression.New(typeof(TRecord)))
};
// Create expression to split string
DelimitedRecordAttribute delimitedRecordAttribute = (DelimitedRecordAttribute)_recordAttribute;
Expression seperatorArray = Expression.NewArrayInit(typeof(String), Expression.Constant(delimitedRecordAttribute.Delimiter));
expressions.Add(Expression.Assign(stringsExpression, Expression.Call(lineExpression, typeof(String).GetMethod("Split", new Type[] { typeof(String[]), typeof(StringSplitOptions) }), seperatorArray, Expression.Constant(StringSplitOptions.None))));
int i = 0;
foreach (PropertyInfo propertyInfo in typeof(TRecord).GetProperties())
{
DelimitedFieldAttribute delimitedFieldAttribute = propertyInfo.GetCustomAttribute <DelimitedFieldAttribute>(false);
if (delimitedFieldAttribute == null)
{
// If a property does not have a DelimitedFieldAttribute then we can simply skip it.
break;
}
expressions.AddRange(CreateFieldExpression(propertyInfo, delimitedFieldAttribute, returnExpression, Expression.ArrayIndex(stringsExpression, Expression.Constant(i))));
i++;
}
expressions.Add(returnExpression);
Expression body = Expression.Block(new List <ParameterExpression> {
returnExpression, stringsExpression
}, expressions);
LambdaExpression lambda = Expression.Lambda <Func <String, TRecord> >(body, lineExpression);
return((Func <String, TRecord>)lambda.Compile());
}
private static Func <String, TRecord> CreateLineParser(IRecordAttribute attribute)
{
ParameterExpression lineExpression = Expression.Parameter(typeof(String), "line");
ParameterExpression returnExpression = Expression.Variable(typeof(TRecord), "ret");
ParameterExpression stringsExpression = Expression.Variable(typeof(String[]), "strings");
List <Expression> expressions =
new List <Expression> {
Expression.Assign(returnExpression, Expression.New(typeof(TRecord)))
};
if (attribute.GetType() == typeof(DelimitedRecordAttribute))
{
DelimitedRecordAttribute delimitedRecordAttribute = (DelimitedRecordAttribute)attribute;
Expression seperatorArray = Expression.NewArrayInit(typeof(String), Expression.Constant(delimitedRecordAttribute.Delimiter));
expressions.Add(Expression.Assign(stringsExpression, Expression.Call(lineExpression, typeof(String).GetMethod("Split", new[] { typeof(String[]), typeof(StringSplitOptions) }), seperatorArray, Expression.Constant(StringSplitOptions.None))));
}
int i = 0;
foreach (PropertyInfo propertyInfo in typeof(TRecord).GetProperties())
{
DelimitedFieldAttribute delimitedFieldAttribute = propertyInfo.GetCustomAttribute <DelimitedFieldAttribute>(false);
FixedWidthFieldAttribute fixedWidthFieldAttribute = propertyInfo.GetCustomAttribute <FixedWidthFieldAttribute>(false);
if (delimitedFieldAttribute == null && fixedWidthFieldAttribute == null)
{
// If property has no derivative of FieldAttribute then we do not include it in parsing.
break;
}
else if (delimitedFieldAttribute != null && attribute.GetType() != typeof(DelimitedRecordAttribute))
{
throw new Exception($"{propertyInfo.Name} cannot have a DelimitedField attribute.");
}
else if (fixedWidthFieldAttribute != null && attribute.GetType() != typeof(FixedWidthRecordAttribute))
{
throw new Exception($"{propertyInfo.Name} cannot have a FixedWidthField attribute.");
}
if (delimitedFieldAttribute != null)
{
//If we are missing delimiters then we assume that it is missing.
Expression valueExpression = Expression.Condition(Expression.GreaterThan(Expression.ArrayLength(stringsExpression), Expression.Constant(i)), Expression.ArrayIndex(stringsExpression, Expression.Constant(i)), Expression.Constant(""));
expressions.AddRange(CreateFieldExpression(propertyInfo, delimitedFieldAttribute, returnExpression, valueExpression));
i++;
}
else
{
Expression substring = Expression.Call(lineExpression, typeof(string).GetMethod("Substring", new[] { typeof(int), typeof(int) }) ?? throw new InvalidOperationException(), Expression.Constant(i), Expression.Constant(fixedWidthFieldAttribute.FieldSize));
expressions.AddRange(CreateFieldExpression(propertyInfo, fixedWidthFieldAttribute, returnExpression, substring));
i += fixedWidthFieldAttribute.FieldSize;
}
}
expressions.Add(returnExpression);
Expression body = Expression.Block(new List <ParameterExpression> {
returnExpression, stringsExpression
}, expressions);
LambdaExpression lambda = Expression.Lambda <Func <String, TRecord> >(body, lineExpression);
return((Func <String, TRecord>)lambda.Compile());
}
