I have the following tables:
Table1
{
Code //string
Desc //string
}
Table2
{
Code //string
Value //decimal?
}
I need to Left Join the tables and for each Table2 Code/Value missing I want to show Code = Table1.Code, Desc = Table1.Desc and Value = null or blank.
I tryied the following lambda expression:
var result = Table1.GroupJoin(
Table2,
x => x.Code,
y => y.Code,
(x, y) => g
.Select(c => new { x.Code, x.Desc, Value = y.Value })
.DefaultIfEmpty(new { x.Code, x.Desc, Value = null }))
.SelectMany(g => g);
and got these errors:
The type arguments for method 'System.Linq.Enumerable.DefaultIfEmpty(System.Collections.Generic.IEnumerable, TSource)' cannot be inferred from the usage. Try specifying the type arguments explicitly.
Cannot assign to anonymous type property
So, I changed ...DefaultIfEmpty... Value = 0 }...
并得到以下错误：'System.Collections.Generic.IEnumerable'不包含'DefaultIfEmpty'的定义，最佳扩展方法重载'System.Linq.Queryable.DefaultIfEmpty（System.Linq.IQueryable，TSource）'有一些无效论点
实例参数：无法从“ System.Collections.Generic.IEnumerable”转换为“ System.Linq.IQueryable”
有解决错误的想法吗？
您只需要null在匿名类型初始值设定项中指定值的类型：
.DefaultIfEmpty(new { x.Code, x.Desc, Value = (decimal?) null }))
使用0时，您正在创建一个单独的匿名类型，该类型的Value属性类型为int，而不是decimal?。
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