如何在C#中添加记录时处理数据表中的唯一约束异常 [英] How to handle unique constraint exception in datatable while adding record in C#

问题描述

我像这样向数据表添加了唯一约束

I have added unique constraint to datatable like this

DataTable dtemp
private void TempTable() 
{
 dtemp = new DataTable("Temp");
 dtemp.Columns.Add(new DataColumn("Table", typeof(int)));
 dtemp.Columns.Add(new DataColumn("Capacity", typeof(int)));
 UniqueConstraint TableUnique = new UniqueConstraint(new DataColumn[] { dtemp.Columns["Table"] });
 dtemp.Constraints.Add(TableUnique);
}       

当我尝试添加相同的记录时，它不会去捕获块，而是会突然退出程序并在 Visual Studio 中给出唯一约束未处理的异常.

When I try to add same record, instead of going to catch block, it simply exit the program abruptly and gives unique constraint unhandled exception in the visual studio.

private void GetTable()
    {
        try
        { 
            dtemp.Rows.Add(mTable.TableID,mTable.Capacity);
        }
        catch(SqlException ee)
        {
            if (ee.Number == 2627)
            {
                MessageBox.Show("Sorry, This Table Is Already Reserved!");
                if (Con.State == ConnectionState.Open) { Con.Close(); }
                return;
            }
            MessageBox.Show("Exception: " + ee.Message);
        } 

谁能告诉我如何处理这个异常?

Can anyone please tell me how to handle this exception?

推荐答案

由于您在本地 DataTable 中定义了约束，因此您正试图捕获错误类型的异常.而不是 SqlException，一个 ConstraintException 被抛出.

Since you have define your constraint in the local DataTable, you're trying to catch the wrong type of exception. Instead of SqlException, a ConstraintException is thrown.

立即解决方法是更改​​ try 子句中的异常类型:

An immediate fix would be, to change the type of exception in your try clause:

try
{ 
    dtemp.Rows.Add(mTable.TableID,mTable.Capacity); 
} 
catch (ConstraintException ee) 
{
    // handle the exception here 
}

如果您想在数据库中检查您的约束，那么这就是您想要定义它的地方，而不是在DataTable 中.在这种情况下，SqlException 将被抛出，但仅当您将数据发送到数据库时，而不是在您向 DataTable 添加一行时.

If you want to check your constraint in the database, then that's where you want to define it instead of in the DataTable. In this case, SqlException will get thrown, but only when you send the data to the database, not when you add a row to the DataTable.

这篇关于如何在C#中添加记录时处理数据表中的唯一约束异常的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！