DataAdapter:更新无法找到 TableMapping['Table'] 或 DataTable 'Table' [英] DataAdapter: Update unable to find TableMapping['Table'] or DataTable 'Table'

问题描述

此代码段引发错误:

更新无法在适配器上找到 TableMapping['Table'] 或 DataTable 'Table'.).Update(ds);线

Update unable to find TableMapping['Table'] or DataTable 'Table'.) on adapter.Update(ds); line

为什么会抛出这种类型的错误?

Why it is throwing this type of error?

SqlConnection con = new SqlConnection();
con.ConnectionString = connectionString();

DataSet ds = new DataSet();

string strQuery = "SELECT * FROM Cars";
SqlDataAdapter adapter = new SqlDataAdapter();

adapter.SelectCommand = new SqlCommand(strQuery, con);

SqlCommandBuilder builder = new SqlCommandBuilder(adapter);

adapter.Fill(ds, "Cars");

//Code to modify data in the DataSet
ds.Tables["Cars"].Rows[0]["Brand"] = "NewBrand";

adapter.UpdateCommand = builder.GetUpdateCommand();
adapter.Update(ds);

推荐答案

使用

adapter.Update(ds, "Cars");

改为.

我已经测试过了.我得到了同样的错误，如果我指定表名，它就可以工作.但是，我必须承认我还不知道为什么 DataAdapter 需要知道表名，因为它具有所需的所有信息.如果我使用ds.GetChanges 我得到一行具有正确的表名.

I have tested it. I got the same error without and it works if i specify the tablename. However, i must admit that i yet don't know why the DataAdapter needs to know the table-name since it has all informations it needs. If i useds.GetChanges i get one row with the correct table-name.

更新我在 上什么也没找到MSDN 但最后在源码中找到了(ILSpy).下面是DBDataAdapter.Update(DataSet)的实现:

public override int Update(DataSet dataSet)
{
    return this.Update(dataSet, "Table");
}

因此，如果您不指定表，则使用表名 "Table"，如果您指定了其他表名，则会出现此错误，即真奇怪！

So if you don't specify a table, the table-name "Table" is used and if you've specified a table-name other than that you'll get this error, that's really strange!

我认为造成这种情况的原因是 DataAdapter 无法调用 GetChanges 来确定要更新的表，原因有两个:

I assume that the reason for this is that the DataAdapter cannot call GetChanges to determine the table to update for two reasons:

1. 这将是低效的，因为它需要循环所有表及其所有行以查找具有 RowState 的行！= Unchanged
2. 可能需要更新多个表，因为它们包含已更改的行.DataAdapter 不支持.因此 DataAdapter.Update(DataSet) 假定默认名称 "Table" 为 table-name.

1. It would be inefficient since it needs to loop all tables and all of their rows to find rows with a RowState != Unchanged
2. It's possible that multiple tables needs to be updated since they contain changed rows. That is not supported via DataAdapter. Hence DataAdapter.Update(DataSet) assumes the default name "Table" as table-name.

编辑:但是，也许有人可以解释一下为什么 DataAdapter 不使用 DataSet.Tables[0].TableName 代替.

Edit: However, maybe someone can explain me why the DataAdapter doesn't use DataSet.Tables[0].TableName instead.

所以一般来说，最好的做法是指定要更新的表的名称.

So in general it seems to be best practise to specify the name of the table you want to update.

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