Question

我一直在玩Linq to Sql，但在定义实体之间的关联时，我遇到了一个问题。

我有2个表，1个是包含客户事务的表，另一个是包含事务类型的查找表。例如，事务可以是“CASH”类型，查询表中的值将具有“CASH”主键和“现金支付”描述。

当我运行我的测试程序时，如果我将事务中的主键和查找表更改为整数，则会得到“无法将类型'System.Int32'的对象强制转换为'System.String'”错误，该计划按预期工作。

我很遗憾地遗漏了一些基本的东西，但我不确定是什么。任何帮助表示赞赏。

这是我用来映射表格的代码：

[Table(Name = "customer")]
public class Customer
{
    [Column(IsPrimaryKey = true, Name = "customer_id")]
    public int CustomerID { get; set; }

    private EntitySet<Transaction> _Transactions;

    [Association(Storage = "_Transactions", OtherKey="CustomerID")]
    public EntitySet<Transaction> Transactions
    {
        get { return this._Transactions; }
        set { this._Transactions.Assign(value); }
    }

    public Customer()
    {
        this._Transactions = new EntitySet<Transaction>();
    }
}

[Table(Name = "custtran")]
public class Transaction
{
    [Column(Name = "compno", DbType="smallint")]
    public int CompanyNumber { get; set; }

    [Column(IsPrimaryKey = true, Name = "tran_no")]
    public int TranNo { get; set; }

    [Column(Name = "customer_id")]
    public int CustomerID { get; set; }

    [Column(Name = "tran_type", DbType="char(4)")]
    public string TranType { get; set; }

    private EntityRef<Customer> _Customer;

    [Association(Storage = "_Customer", ThisKey = "CustomerID")]
    public Customer Customer
    {
        get { return this._Customer.Entity; }
        set { this._Customer.Entity = value; }
    }

    private EntitySet<TransactionType> _TransactionTypes;
    [Association(Name="Custtran_TranType", Storage = "_TransactionTypes", IsForeignKey=true,  OtherKey = "TranType")]
    public EntitySet<TransactionType> TransactionTypes
    {
        get { return this._TransactionTypes; }
        set { this._TransactionTypes.Assign(value); }
    }

    public Transaction()
    {
       this._Customer = default(EntityRef<Customer>);
       this._TransactionTypes = new EntitySet<TransactionType>();
    }
}

[Table(Name = "tran_type")]
public class TransactionType
{
    [Column(Name = "compno", DbType = "smallint")]
    public int CompanyNumber { get; set; }

    [Column(IsPrimaryKey = true, Name = "tran_type", DbType="char(4)")]
    public string TranType { get; set; }

    [Column(Name = "description", DbType="Varchar(50)")]
    public string Description { get; set; }

    private EntityRef<Transaction> _Transaction;
    [Association(Name="Custtran_TranType", Storage = "_Transaction", ThisKey = "TranType")]
    public Transaction Transaction
    {
        get { return this._Transaction.Entity; }
        set { this._Transaction.Entity = value; }
    }

    public TransactionType()
    {
        this._Transaction = default(EntityRef<Transaction>);
    }
}

Answer 1

忽略我，我已经回答了我自己的问题。

private EntitySet<TransactionType> _TransactionTypes;
    [Association(Name="Custtran_TranType", Storage = "_TransactionTypes", IsForeignKey=true, ThisKey="TranType", OtherKey = "TranType")]
    public EntitySet<TransactionType> TransactionTypes
    {
        get { return this._TransactionTypes; }
        set { this._TransactionTypes.Assign(value); }
    }

将ThisKey添加到协会，它现在可以正常工作。

Linq to Sql实体关联（非整数主键）

1 个答案: