static LambdaExpression CreateMappingLambda(Type typeT, List <Mapping <Thing, Thing> > mapping)
{
var result = Expression.Parameter(typeof(SqlDataRecord), "rec");
var metaDataParam = Expression.Parameter(typeof(SqlMetaData[]), "metaData");
var item = Expression.Parameter(typeT, "item");
var constructorInfo = typeof(SqlDataRecord).GetConstructor(new[] { typeof(SqlMetaData[]) });
var lines = new List <Expression>
{
Expression.Assign(result, Expression.New(constructorInfo, metaDataParam))
};
var propertiesAndFields = Types.ReadablePropertiesAndFieldsDictionary(typeT);
var setNullMethod = typeof(SqlDataRecord).GetMethod("SetDBNull", new[] { typeof(int) });
Contract.Assert(setNullMethod != null);
foreach (var map in mapping)
{
var col = (Column)map.To;
var setValueExp = SetValue(result, item, map.From, col);
if (setValueExp == null)
{
continue;
}
if (Types.CanBeNull(map.From.Type))
{
lines.Add(Expression.IfThenElse(
Expression.Equal(Expression.PropertyOrField(item, map.From.Name), Expression.Constant(null)),
Expression.Call(result, setNullMethod, Expression.Constant(col.Ordinal)),
setValueExp
));
}
else
{
lines.Add(setValueExp);
}
}
lines.Add(result);
var block = Expression.Block(new[] { result }, lines);
var func = typeof(Func <, ,>).MakeGenericType(typeof(SqlMetaData[]), typeT, typeof(SqlDataRecord));
var lambdaExpression = Expression.Lambda(func, block, metaDataParam, item);
return(lambdaExpression);
}