2

我是新手Dapper和Dapper.Contrib。有一个这样的类，并且数据库中有一个同名的表：

public class Ware
{        
    public int ID { get; set; }
    public string Name { get; set; }
    public short UnitID { get; set; }
    public short TypeID { get; set; }
    public int CableCodeID { get; set; }
    public string Tag1 { get; set; }
    public string Tag2 { get; set; }
    public bool Discontinued { get; set; }
    public decimal Stock { get; set; } //this is not in database. this is helper
    public string UnitCaption { get; set; } //this is not in database. this is helper
    public string TypeCaption { get; set; } //this is not in database. this is helper
    public string FullCaption //this is not in database. this is helper
    {
        get
        {
            return $"{ID} {Name}";
        }
    }
}

我需要将此类的整个列表更新到数据库。我用：

conection.Update(myList); // myList is List<Ware>

但是运行的时候报错：

System.Data.SqlClient.SqlException: 'Invalid column name 'Stock'.'
System.Data.SqlClient.SqlException: 'Invalid column name 'UnitCaption'.'
System.Data.SqlClient.SqlException: 'Invalid column name 'TypeCaption'.'
System.Data.SqlClient.SqlException: 'Invalid column name 'FullCaption'.'

如何解决这个问题？

4

1 回答 1

2

从源代码复制Dapper.Contrib代码：

计算

    [AttributeUsage(AttributeTargets.Property)]
    public class ComputedAttribute : Attribute { }

代码中计算的用法：

private static List<PropertyInfo> ComputedPropertiesCache(Type type)
{
            IEnumerable<PropertyInfo> pi;
            if (ComputedProperties.TryGetValue(type.TypeHandle, out pi))
            {
                return pi.ToList();
            }

            var computedProperties = TypePropertiesCache(type).Where(p => p.GetCustomAttributes(true).Any(a => a is ComputedAttribute)).ToList();

            ComputedProperties[type.TypeHandle] = computedProperties;
            return computedProperties;
}

现在Insert<T>并Update<T>具有以下代码：

var computedProperties = ComputedPropertiesCache(type);

var allPropertiesExceptKeyAndComputed = allProperties.Except(keyProperties.Union(computedProperties)).ToList();

现在allPropertiesExceptKeyAndComputed在代码中进一步处理。

写属性

 public class WriteAttribute : Attribute
 {
    public WriteAttribute(bool write)
    {
       Write = write;
    }
    public bool Write { get; }
}

IsWriteable 在代码中的用法：

 private static List<PropertyInfo> TypePropertiesCache(Type type)
 {
    IEnumerable<PropertyInfo> pis;
    if (TypeProperties.TryGetValue(type.TypeHandle, out pis))
    {
       return pis.ToList();
    }

    var properties = type.GetProperties().Where(IsWriteable).ToArray();
    TypeProperties[type.TypeHandle] = properties;
    return properties.ToList();
 }

 private static bool IsWriteable(PropertyInfo pi)
 {
     var attributes = pi.GetCustomAttributes(typeof(WriteAttribute), false).AsList();
     if (attributes.Count != 1) return true;

     var writeAttribute = (WriteAttribute)attributes[0];
     return writeAttribute.Write;
 }

现在注意ComputedPropertiesCache上面粘贴的用于Computed的函数它调用方法TypePropertiesCache，因此会发生什么，它将排除属性（Write("false")和Computed），但是Write属性是为了从缓存中排除 Type 属性，它是使用创建ConcurrentDictionary的，Computed它是非常适合您的用例。希望它按预期有所帮助。

于 2017-04-10T08:17:19.787 回答