参数化更新

Question

我正在尝试更新访问文件(.accdb)中的记录。我正在尝试使用.net OleDbCommand和OleDbParameters。我还试图使用通用模型，并将所有命令和参数存储在System.Data.Common抽象等效项中，这样我就可以轻松地切换到Server (我确实计划这样做)

，下面是实际使用的命令

编辑2/2/2013-9:10 command.ExecuteNonQuery在名为ExecuteNonQuery()的方法中，connectionString和命令是在DataAccess类构造函数中定义的

public class DataAccess
{

    private string connectionString;
    private DbConnection connection;
    private DbCommand command;
    private DbDataReader reader;
    private DataTable data;

    public DataAccess()
    {
        connectionString = ConfigurationSettings.AppSettings["ConnectionString"];

        switch (ConfigurationSettings.AppSettings["DataBaseType"])
        {
            case "oledb":
                connection = new OleDbConnection(connectionString);
                command = new OleDbCommand(string.Empty, (OleDbConnection)connection);
                break;
            case "SQL":                 
                connection = new SqlConnection(connectionString);
                command = new SqlCommand(string.Empty, (SqlConnection)connection);
                break;
            default:
                break;
        }

    }

    public void ExecuteNonQuery(string SQL, params DbParameter[] parameters)
    {
        command.CommandType = CommandType.Text;
        command.CommandText = SQL;
        command.Parameters.AddRange(parameters);

        try
        {
            command.Connection.Open();

            try
            {
                command.ExecuteNonQuery();
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                command.Connection.Close();
            }
        }
        catch (Exception ex)
        {
            throw ex;
        }
    }

    public DbParameter NewParameter(string name, object value)
    {
        DbParameter param;

        switch (ConfigurationSettings.AppSettings["DataBaseType"])
        {
            case "oledb":
                param = new OleDbParameter(name, value);
                break;
            case "SQL":
                param = new SqlParameter(name, value);
                break;
            default:
                param = null;
                break;
        }

        return param;
    }

--这些是App.Config文件中的属性

<add key="DataBaseType" value="oledb"/>

<add key="ConnectionString" value="Provider=Microsoft.ACE.OLEDB.12.0;Data Source=data.accdb"/>

现在的问题是，当在update语句中使用参数时，更新永远不会发生，也不会引发错误。这是它的代码。

编辑2/2/2013-9:10函数DataAccess.NewParameter在第一个代码块中

DALayer.ExecuteNonQuery("UPDATE TileTypes SET Title = @Title, Picture = @Picture, Color = @Color WHERE ID = @ID",
 DALayer.NewParameter("@Title", titleTextBox.Text.Trim()),
 DALayer.NewParameter("@Picture", typePictureBox.ImageLocation),
 DALayer.NewParameter("@Color", colorButton.BackColor.ToArgb()),
 DALayer.NewParameter("@ID", id));

我已经将查询复制到access中，并将所有参数名称替换为传递的实际数据，这很好。我尝试将SQL文本中的所有参数替换为？性格没有效果。我试图将方括号[]中的所有表名和列名附在一起，但也没有任何效果。

• ID是一个AutoNumber字段
• 标题是文本字段。
• 图片是文本字段。
• 颜色是一个长整数域。

以下是直接从Visual监视窗口中的参数复制的一些示例数据：

• “编辑”(标题)
• -1 (颜色)
• "data\images\Edit_000000.jpg“(图片)
• 740 (id)

该ID确实存在于数据库中，并在查询执行后保持不变。

编辑2/2/2013-9:10我不知道如何检查哪个数据库实际上正在被更新，我唯一能想到的是，使用相同的连接字符串和连接对象，我用相同的ExecuteNonquery方法做了一个insert语句，它在我正在查看的数据库中工作。update语句就像这样工作得很好(没有参数)：

DALayer.ExecuteNonQuery("UPDATE TileTypes SET Title = '" + titleTextBox.Text + 
"', Color = " + colorButton.BackColor.ToArgb() + ", Picture = '" + 
imageLocation + "' WHERE ID = " + id);

编辑2/2/2013 - 9:41pm我使用everything.exe搜索我的计算机上的所有data.accdb文件，除了原始的data.accdb文件之外，我没有找到实际的.accdb文件，但是我确实找到了这些.lnk文件，我认为它们不可能改变这个过程，但我还是要提到它。

data.accdb.LNK

Answer 1

您试图做的是我过去也做过的事情，但是允许连接到OleDB (例如Access、Visual FoxPro等)、Server、SyBase SQLAnywhere，或者我的实现可能会对您有所帮助。首先，用于连接公共接口上的工作的每个元素，如IDbConnection、IDbCommand、IDbParameter等。

下面是我最初如何构造这种多数据库连接类型的一小部分内容。我已经删除了一堆，并没有实际测试这个剥离版本，但它应该是您运行的一个很好的基线。

前提是基线"MyConnection“几乎是抽象的，但是有一些属性和一些在任何子类定义下都存在的”公共“方法。由此，每个函数和参数类型都是基于“i”面的，而不是特定的。但是，每个派生程序都将创建自己的适当类型。这就消除了“大小写”的需要。希望这有助于您与您的数据访问层的开发。

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;

// for OleDB (Access, VFP, etc)
using System.Data.OleDb;
// for SQL-Server
using System.Data.SqlClient;

namespace DataMgmt
{
    public class MyConnection
    {
        // no matter the connection to server, it will require some "handle"
        // that is of type "IDbConnection"
        protected IDbConnection sqlConnectionHandle;

        // when querying, ANY query could have an exception that needs to have
        // possible further review for handling
        public Exception LastException
        { get; protected set; }

        // When calling an execute command (select, insert, update, delete), 
        // they all can return how many rows affected
        public int RowsAffectedByQuery
        { get; protected set; }

        // different databases could have different connection strings. Make
        // virtual and throw exception so sub-classed must return proper formatted.
        public virtual string GetConnectionString()
        { throw new Exception("GetConnectionString() method must be overridden."); }

        // each has its own "IDbConnection" type too
        protected virtual IDbConnection SQLConnectionHandle()
        { return sqlConnectionHandle; }

        public virtual IDbCommand GetSQLDbCommand()
        { throw new Exception("GetSQLDbCommand() method must be overridden."); }

        // generic routine to get a data parameter...
        public virtual IDbDataParameter AddDbParmSpecificValue(string ParmName, object UnknownValue)
        { throw new Exception("AddDbParmSpecificValue() method must be overwritten per specific connection."); }

        // generic "Connection" since they are all based on IDbCommand...
        public override bool SQLConnect()
        {
            // pre-blank exception in case remnant from previous activity
            LastException = null;

            if (sqlConnectionHandle.State != System.Data.ConnectionState.Open)
                try
                {
                    // if not open, always make sure we get updated connection string
                    // if ever changed by some other "unknown" condition...
                    sqlConnectionHandle.ConnectionString = GetConnectionString();
                    sqlConnectionHandle.Open();
                }
                catch (Exception ex)
                {
                    // Preserve in generic sqlException" property for analysis OUTSIDE this function
                    LastException = ex;
                }

            // if NOT connected, display message to user and set error code and exception
            if (sqlConnectionHandle.State != System.Data.ConnectionState.Open)
                LastException = new Exception("Unable to open database connection.");

            // return if it IS successful at opening the connection (or was already open)
            return sqlConnectionHandle.State == System.Data.ConnectionState.Open;
        }

        // likewise disconnect could be common
        public void SQLDisconnect()
        {
            if (sqlConnectionHandle != null)
                if (sqlConnectionHandle.State == ConnectionState.Open)
                    sqlConnectionHandle.Close();
        }


        public bool SqlExecNonQuery( IDbCommand SQLCmd, DataTable oTbl)
        {
            // pre-clear exception
            LastException = null;

            // fill the table...
            SQLConnect();
            try
            {
                RowsAffectedByQuery = SQLCmd.ExecuteNonQuery();
            }
            catch (Exception e)
            {
                LastException = e;
                throw e;
            }
            finally
            {
                SQLDisconnect();
            }

            // Its all ok if no exception error
            return LastException == null;
        }

    }


    // Now, build your connection manager per specific type
    public class MyAccessConnection : MyConnection
    {
        public MyAccessConnection()
        {   sqlConnectionHandle =  new OleDbConnection();   }

        public override string GetConnectionString()
        {   return "Your Connection String from AppSettings.. any changes if OleDb vs SQL"; }

        public override IDbCommand GetSQLDbCommand()
        {   return new OleDbCommand( "", (OleDbConnection)sqlConnectionHandle ); }

        public override IDbDataParameter AddDbParmSpecificValue(string ParmName, object UnknownValue)
        {   return new OleDbParameter( ParmName, UnknownValue );    }

    }

    public class MySQLConnection : MyConnection
    {
        public MySQLConnection()
        {   sqlConnectionHandle = new SqlConnection();  }

        public override string GetConnectionString()
        { return "Your Connection String from AppSettings... any alterations needed??? "; }

        public override IDbCommand GetSQLDbCommand()
        { return new SqlCommand ("", (SqlConnection)sqlConnectionHandle); }

        public override IDbDataParameter AddDbParmSpecificValue(string ParmName, object UnknownValue)
        { return new SqlParameter(ParmName, UnknownValue); }
    }



    // Now to implement... pick one... Access or SQL-Server for derivation...
    public class MyDataLayer : MyAccessConnection
    {
        public void SomeSQLCall()
        {
            IDbCommand sqlcmd = GetSQLDbCommand();
            sqlcmd.CommandText = "UPDATE TileTypes SET Title = @Title, "
                                + "Picture = @Picture, "
                                + "Color = @Color "
                                + "WHERE ID = @ID";
            sqlcmd.Parameters.Add( AddDbParmSpecificValue( "@Title", titleTextBox.Text.Trim() ));
            sqlcmd.Parameters.Add( AddDbParmSpecificValue( "@Picture", typePictureBox.ImageLocation) );
            sqlcmd.Parameters.Add( AddDbParmSpecificValue( "@Color", colorButton.BackColor.ToArgb()) );
            sqlcmd.Parameters.Add( AddDbParmSpecificValue(  "@ID", id));

        if( SqlExecNonQuery(sqlcmd))
            // Good to go
            DoSomethingWithTheData;
        else
            // Notify of whatever error thrown....

        }
    }
}

所以..。如您所见，我的最后一个类具体是从Access或SQL派生的。然后，我可以创建我的方法来获取数据，调用更新等等。获取一个SQL命令(该命令返回正确的类型，并自动附加到其相应的“连接句柄”对象)，准备文本，添加参数，执行它。