因存储过程参数类型不匹配而造成OleDbCommand的不可用

    技术2022-05-11  8

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    (续 因存储过程参数类型不匹配而造成OleDbCommand的不可用一)

     

    表格二,断点二处的内存状况

    -

    comm

    {System.Data.OleDb.OleDbCommand}

    System.Data.OleDb.OleDbCommand

     

    transaction

    null

    System.Data.OleDb.OleDbTransaction

     

    cmdText

    Test

    string

     

    cmdType

    StoredProcedure

    System.Data.CommandType

     

    updatedRowSource

    Both

    System.Data.UpdateRowSource

     

    commandTimeout

    30

    int

    +

    icommandText

    {System.__ComObject}

    System.Data.Common.UnsafeNativeMethods.ICommandText

     

    handle_Accessor

    1

    int

     

    commandBehavior

    Default

    System.Data.CommandBehavior

    +

    dbBindings

    {System.Data.OleDb.DBBindings}

    System.Data.OleDb.DBBindings

     

    canceling

    FALSE

    bool

     

    isPrepared

    FALSE

    bool

     

    executeQuery

    FALSE

    bool

     

    computedParameters

    FALSE

    bool

     

    designTimeVisible

    FALSE

    bool

     

    cmdState

    0

    int

     

    recordsAffected

    -1

    int

     

    CommandText

    Test

    string

     

    CommandTimeout

    30

    int

     

    CommandType

    StoredProcedure

    System.Data.CommandType

     

    DesignTimeVisible

    TRUE

    bool

     

    IsClosed

    TRUE

    bool

     

    Transaction

    null

    System.Data.OleDb.OleDbTransaction

     

    UpdatedRowSource

    Both

    System.Data.UpdateRowSource

     

    由上面表格一和表格二可发现,在OleDbCommand第一次执行ExecuteNoQuery()时,将改变其内部icommandTextdbBindingshandle_Accessor3个私有属性。并且经过观察发现,只有CommandText被赋予与原来不同的值时才把以上3个私有属性的值恢复到原来的默认值(即icommandTextnulldbBindingsnullhandle_Accessor0)。

    这时我们把上面的代码稍作修改,在第一个try块里给原本为存储过程参数Age赋与一个不能转换为整数值的字符串:

    using System;

    using System.Data;

    using System.Data.OleDb;

     

    namespace testCommand

    {

        class Class1

        {

            [STAThread]

            static void Main (string[] args)

            {

                OleDbConnection conn=new OleDbConnection("xxx");

                conn.Open();

                OleDbCommand comm=new OleDbCommand("Test",conn);

                comm.CommandType=CommandType.StoredProcedure;

     

                OleDbCommandBuilder.DeriveParameters(comm);

     

                try

                {

                    comm.Parameters["Name"].Value="my name";

                    comm.Parameters["Age"].Value=(object)”aa”;

                    comm.ExecuteNonQuery();  //断点三,此处内存状况见表一

                }

                catch(Exception err)

                {

                    Console.WriteLine(

                        err.TargetSite+"--"+err.StackTrace+"--"+

                        err.Source+"--"+err.Message+"--"+

                        err.GetType().ToString());

                }

               

                //TODO: 增加对OleDbCommand进行修复的语句

               

                try

                {

                    comm.Parameters["Name"].Value="my name";

                    comm.Parameters["Age"].Value=(object)11;

                    comm.ExecuteNonQuery();  // </script> <script type="text/javascript" src="http://pagead2.googlesyndication.com/pagead/show_ads.js"> </script>

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