C# implementiert Methoden für den Zugriff auf die SQLite-Datenbank basierend auf der SQLiteHelper-Klasse, die der SqlHelper-Klasse ähnelt

Das Beispiel in diesem Artikel beschreibt, wie C# den Zugriff auf die SQLite-Datenbank basierend auf der SQLiteHelper-ähnlichen SqlHelper-Klasse implementiert. Teilen Sie es als Referenz mit allen. Die Details lauten wie folgt:

Diese Klasse wird von mir nicht implementiert. Die ursprüngliche englische Adresse lautet http://www.eggheadcafe.com/articles/20050315.asp. Die Methode zur Analyse von SQL-Anweisungsparametern Der ursprüngliche Artikel wurde hier geändert. Ändern Sie den Namen in AttachParameters, ändern Sie seinen Modifikator in privat, übergeben Sie den Befehl direkt an diese Methode und binden Sie die Parameter direkt an den Befehl. Der geänderte Code lautet wie folgt:

using System;
using System.Data;
using System.Text.RegularExpressions;
using System.Xml;
using System.IO;
using System.Collections;
using System.Data.SQLite;
namespace DBUtility.SQLite
{
 /// <summary>
 /// SQLiteHelper is a utility class similar to "SQLHelper" in MS
 /// Data Access Application Block and follows similar pattern.
 /// </summary>
 public class SQLiteHelper
 {
  /// <summary>
  /// Creates a new <see cref="SQLiteHelper"/> instance. The ctor is marked private since all members are static.
  /// </summary>
  private SQLiteHelper()
  {
  }
  /// <summary>
  /// Creates the command.
  /// </summary>
  /// <param name="connection">Connection.</param>
  /// <param name="commandText">Command text.</param>
  /// <param name="commandParameters">Command parameters.</param>
  /// <returns>SQLite Command</returns>
  public static SQLiteCommand CreateCommand(SQLiteConnection connection, string commandText, params SQLiteParameter[] commandParameters)
  {
   SQLiteCommand cmd = new SQLiteCommand(commandText, connection);
   if (commandParameters.Length > 0)
   {
    foreach (SQLiteParameter parm in commandParameters)
     cmd.Parameters.Add(parm);
   }
   return cmd;
  }
  /// <summary>
  /// Creates the command.
  /// </summary>
  /// <param name="connectionString">Connection string.</param>
  /// <param name="commandText">Command text.</param>
  /// <param name="commandParameters">Command parameters.</param>
  /// <returns>SQLite Command</returns>
  public static SQLiteCommand CreateCommand(string connectionString, string commandText, params SQLiteParameter[] commandParameters)
  {
   SQLiteConnection cn = new SQLiteConnection(connectionString);
   SQLiteCommand cmd = new SQLiteCommand(commandText, cn);
   if (commandParameters.Length > 0)
   {
    foreach (SQLiteParameter parm in commandParameters)
     cmd.Parameters.Add(parm);
   }
   return cmd;
  }
  /// <summary>
  /// Creates the parameter.
  /// </summary>
  /// <param name="parameterName">Name of the parameter.</param>
  /// <param name="parameterType">Parameter type.</param>
  /// <param name="parameterValue">Parameter value.</param>
  /// <returns>SQLiteParameter</returns>
  public static SQLiteParameter CreateParameter(string parameterName, System.Data.DbType parameterType, object parameterValue)
  {
   SQLiteParameter parameter = new SQLiteParameter();
   parameter.DbType = parameterType;
   parameter.ParameterName = parameterName;
   parameter.Value = parameterValue;
   return parameter;
  }
  /// <summary>
  /// Shortcut method to execute dataset from SQL Statement and object[] arrray of parameter values
  /// </summary>
  /// <param name="connectionString">SQLite Connection string</param>
  /// <param name="commandText">SQL Statement with embedded "@param" style parameter names</param>
  /// <param name="paramList">object[] array of parameter values</param>
  /// <returns></returns>
  public static DataSet ExecuteDataSet(string connectionString, string commandText, object[] paramList)
  {
   SQLiteConnection cn = new SQLiteConnection(connectionString);
   SQLiteCommand cmd = cn.CreateCommand();
 
   cmd.CommandText = commandText;
   if (paramList != null)
   {
    AttachParameters(cmd,commandText, paramList);
   }
   DataSet ds = new DataSet();
   if (cn.State == ConnectionState.Closed)
    cn.Open();
   SQLiteDataAdapter da = new SQLiteDataAdapter(cmd);
   da.Fill(ds);
   da.Dispose();
   cmd.Dispose();
   cn.Close();
   return ds;
  }
  /// <summary>
  /// Shortcut method to execute dataset from SQL Statement and object[] arrray of parameter values
  /// </summary>
  /// <param name="cn">Connection.</param>
  /// <param name="commandText">Command text.</param>
  /// <param name="paramList">Param list.</param>
  /// <returns></returns>
  public static DataSet ExecuteDataSet(SQLiteConnection cn, string commandText, object[] paramList)
  {
   SQLiteCommand cmd = cn.CreateCommand();
 
   cmd.CommandText = commandText;
   if (paramList != null)
   {
    AttachParameters(cmd,commandText, paramList);
   }
   DataSet ds = new DataSet();
   if (cn.State == ConnectionState.Closed)
    cn.Open();
   SQLiteDataAdapter da = new SQLiteDataAdapter(cmd);
   da.Fill(ds);
   da.Dispose();
   cmd.Dispose();
   cn.Close();
   return ds;
  }
  /// <summary>
  /// Executes the dataset from a populated Command object.
  /// </summary>
  /// <param name="cmd">Fully populated SQLiteCommand</param>
  /// <returns>DataSet</returns>
  public static DataSet ExecuteDataset(SQLiteCommand cmd)
  {
   if (cmd.Connection.State == ConnectionState.Closed)
    cmd.Connection.Open();
   DataSet ds = new DataSet();
   SQLiteDataAdapter da = new SQLiteDataAdapter(cmd);
   da.Fill(ds);
   da.Dispose();
   cmd.Connection.Close();
   cmd.Dispose();
   return ds;
  }
  /// <summary>
  /// Executes the dataset in a SQLite Transaction
  /// </summary>
  /// <param name="transaction">SQLiteTransaction. Transaction consists of Connection, Transaction, /// and Command, all of which must be created prior to making this method call. </param>
  /// <param name="commandText">Command text.</param>
  /// <param name="commandParameters">Sqlite Command parameters.</param>
  /// <returns>DataSet</returns>
  /// <remarks>user must examine Transaction Object and handle transaction.connection .Close, etc.</remarks>
  public static DataSet ExecuteDataset(SQLiteTransaction transaction, string commandText, params SQLiteParameter[] commandParameters)
  {
   if (transaction == null) throw new ArgumentNullException("transaction");
   if (transaction != null && transaction.Connection == null) throw new ArgumentException("The transaction was rolled back or committed, please provide an open transaction.", "transaction");
   IDbCommand cmd = transaction.Connection.CreateCommand();
   cmd.CommandText = commandText;
   foreach (SQLiteParameter parm in commandParameters)
   {
    cmd.Parameters.Add(parm);
   }
   if (transaction.Connection.State == ConnectionState.Closed)
    transaction.Connection.Open();
   DataSet ds = ExecuteDataset((SQLiteCommand)cmd);
   return ds;
  }
  /// <summary>
  /// Executes the dataset with Transaction and object array of parameter values.
  /// </summary>
  /// <param name="transaction">SQLiteTransaction. Transaction consists of Connection, Transaction, /// and Command, all of which must be created prior to making this method call. </param>
  /// <param name="commandText">Command text.</param>
  /// <param name="commandParameters">object[] array of parameter values.</param>
  /// <returns>DataSet</returns>
  /// <remarks>user must examine Transaction Object and handle transaction.connection .Close, etc.</remarks>
  public static DataSet ExecuteDataset(SQLiteTransaction transaction, string commandText, object[] commandParameters)
  {
   if (transaction == null) throw new ArgumentNullException("transaction");
   if (transaction != null && transaction.Connection == null) throw new ArgumentException("The transaction was rolled back or committed,               please provide an open transaction.", "transaction");
   IDbCommand cmd = transaction.Connection.CreateCommand();
   cmd.CommandText = commandText;
   AttachParameters((SQLiteCommand)cmd,cmd.CommandText, commandParameters);
   if (transaction.Connection.State == ConnectionState.Closed)
    transaction.Connection.Open();
   DataSet ds = ExecuteDataset((SQLiteCommand)cmd);
   return ds;
  }
  #region UpdateDataset
  /// <summary>
  /// Executes the respective command for each inserted, updated, or deleted row in the DataSet.
  /// </summary>
  /// <remarks>
  /// e.g.: 
  /// UpdateDataset(conn, insertCommand, deleteCommand, updateCommand, dataSet, "Order");
  /// </remarks>
  /// <param name="insertCommand">A valid SQL statement to insert new records into the data source</param>
  /// <param name="deleteCommand">A valid SQL statement to delete records from the data source</param>
  /// <param name="updateCommand">A valid SQL statement used to update records in the data source</param>
  /// <param name="dataSet">The DataSet used to update the data source</param>
  /// <param name="tableName">The DataTable used to update the data source.</param>
  public static void UpdateDataset(SQLiteCommand insertCommand, SQLiteCommand deleteCommand, SQLiteCommand updateCommand, DataSet dataSet, string tableName)
  {
   if (insertCommand == null) throw new ArgumentNullException("insertCommand");
   if (deleteCommand == null) throw new ArgumentNullException("deleteCommand");
   if (updateCommand == null) throw new ArgumentNullException("updateCommand");
   if (tableName == null || tableName.Length == 0) throw new ArgumentNullException("tableName");
   // Create a SQLiteDataAdapter, and dispose of it after we are done
   using (SQLiteDataAdapter dataAdapter = new SQLiteDataAdapter())
   {
    // Set the data adapter commands
    dataAdapter.UpdateCommand = updateCommand;
    dataAdapter.InsertCommand = insertCommand;
    dataAdapter.DeleteCommand = deleteCommand;
    // Update the dataset changes in the data source
    dataAdapter.Update(dataSet, tableName);
    // Commit all the changes made to the DataSet
    dataSet.AcceptChanges();
   }
  }
  #endregion
 
 
  /// <summary>
  /// ShortCut method to return IDataReader
  /// NOTE: You should explicitly close the Command.connection you passed in as
  /// well as call Dispose on the Command after reader is closed.
  /// We do this because IDataReader has no underlying Connection Property.
  /// </summary>
  /// <param name="cmd">SQLiteCommand Object</param>
  /// <param name="commandText">SQL Statement with optional embedded "@param" style parameters</param>
  /// <param name="paramList">object[] array of parameter values</param>
  /// <returns>IDataReader</returns>
  public static IDataReader ExecuteReader(SQLiteCommand cmd, string commandText, object[] paramList)
  {
   if (cmd.Connection == null)
    throw new ArgumentException("Command must have live connection attached.", "cmd");
   cmd.CommandText = commandText;
   AttachParameters(cmd,commandText, paramList);
   if (cmd.Connection.State == ConnectionState.Closed)
    cmd.Connection.Open();
   IDataReader rdr = cmd.ExecuteReader(CommandBehavior.CloseConnection);
   return rdr;
  }
  /// <summary>
  /// Shortcut to ExecuteNonQuery with SqlStatement and object[] param values
  /// </summary>
  /// <param name="connectionString">SQLite Connection String</param>
  /// <param name="commandText">Sql Statement with embedded "@param" style parameters</param>
  /// <param name="paramList">object[] array of parameter values</param>
  /// <returns></returns>
  public static int ExecuteNonQuery(string connectionString, string commandText, params object[] paramList)
  {
   SQLiteConnection cn = new SQLiteConnection(connectionString);
   SQLiteCommand cmd = cn.CreateCommand();
   cmd.CommandText = commandText;
   AttachParameters(cmd,commandText, paramList);
   if (cn.State == ConnectionState.Closed)
    cn.Open();
   int result = cmd.ExecuteNonQuery();
   cmd.Dispose();
   cn.Close();
   return result;
  }
 
  public static int ExecuteNonQuery(SQLiteConnection cn, string commandText, params object[] paramList)
  {
   SQLiteCommand cmd = cn.CreateCommand();
   cmd.CommandText = commandText;
   AttachParameters(cmd,commandText, paramList);
   if (cn.State == ConnectionState.Closed)
    cn.Open();
   int result = cmd.ExecuteNonQuery();
   cmd.Dispose();
   cn.Close();
   return result;
  }
  /// <summary>
  /// Executes non-query sql Statment with Transaction
  /// </summary>
  /// <param name="transaction">SQLiteTransaction. Transaction consists of Connection, Transaction, /// and Command, all of which must be created prior to making this method call. </param>
  /// <param name="commandText">Command text.</param>
  /// <param name="paramList">Param list.</param>
  /// <returns>Integer</returns>
  /// <remarks>user must examine Transaction Object and handle transaction.connection .Close, etc.</remarks>
  public static int ExecuteNonQuery(SQLiteTransaction transaction, string commandText, params object[] paramList)
  {
   if (transaction == null) throw new ArgumentNullException("transaction");
   if (transaction != null && transaction.Connection == null) throw new ArgumentException("The transaction was rolled back or committed,              please provide an open transaction.", "transaction");
   IDbCommand cmd = transaction.Connection.CreateCommand();
   cmd.CommandText = commandText;
   AttachParameters((SQLiteCommand)cmd,cmd.CommandText, paramList);
   if (transaction.Connection.State == ConnectionState.Closed)
    transaction.Connection.Open();
   int result = cmd.ExecuteNonQuery();
   cmd.Dispose();
   return result;
  }
 
  /// <summary>
  /// Executes the non query.
  /// </summary>
  /// <param name="cmd">CMD.</param>
  /// <returns></returns>
  public static int ExecuteNonQuery(IDbCommand cmd)
  {
   if (cmd.Connection.State == ConnectionState.Closed)
    cmd.Connection.Open();
   int result = cmd.ExecuteNonQuery();
   cmd.Connection.Close();
   cmd.Dispose();
   return result;
  }
  /// <summary>
  /// Shortcut to ExecuteScalar with Sql Statement embedded params and object[] param values
  /// </summary>
  /// <param name="connectionString">SQLite Connection String</param>
  /// <param name="commandText">SQL statment with embedded "@param" style parameters</param>
  /// <param name="paramList">object[] array of param values</param>
  /// <returns></returns>
  public static object ExecuteScalar(string connectionString, string commandText, params object[] paramList)
  {
   SQLiteConnection cn = new SQLiteConnection(connectionString);
   SQLiteCommand cmd = cn.CreateCommand();
   cmd.CommandText = commandText;
   AttachParameters(cmd,commandText, paramList);
   if (cn.State == ConnectionState.Closed)
    cn.Open();
   object result = cmd.ExecuteScalar();
   cmd.Dispose();
   cn.Close();
   return result;
  }
  /// <summary>
  /// Execute XmlReader with complete Command
  /// </summary>
  /// <param name="command">SQLite Command</param>
  /// <returns>XmlReader</returns>
  public static XmlReader ExecuteXmlReader(IDbCommand command)
  { // open the connection if necessary, but make sure we 
   // know to close it when we�re done.
   if (command.Connection.State != ConnectionState.Open)
   {
    command.Connection.Open();
   }
   // get a data adapter 
   SQLiteDataAdapter da = new SQLiteDataAdapter((SQLiteCommand)command);
   DataSet ds = new DataSet();
   // fill the data set, and return the schema information
   da.MissingSchemaAction = MissingSchemaAction.AddWithKey;
   da.Fill(ds);
   // convert our dataset to XML
   StringReader stream = new StringReader(ds.GetXml());
   command.Connection.Close();
   // convert our stream of text to an XmlReader
   return new XmlTextReader(stream);
  }
 
  /// <summary>
  /// Parses parameter names from SQL Statement, assigns values from object array , /// and returns fully populated ParameterCollection.
  /// </summary>
  /// <param name="commandText">Sql Statement with "@param" style embedded parameters</param>
  /// <param name="paramList">object[] array of parameter values</param>
  /// <returns>SQLiteParameterCollection</returns>
  /// <remarks>Status experimental. Regex appears to be handling most issues. Note that parameter object array must be in same ///order as parameter names appear in SQL statement.</remarks>
  private static SQLiteParameterCollection AttachParameters(SQLiteCommand cmd, string commandText, params object[] paramList)
  {
   if (paramList == null || paramList.Length == 0) return null;
   SQLiteParameterCollection coll = cmd.Parameters;
   string parmString = commandText.Substring(commandText.IndexOf("@"));
   // pre-process the string so always at least 1 space after a comma.
   parmString = parmString.Replace(",", " ,");
   // get the named parameters into a match collection
   string pattern = @"(@)\S*(.*?)\b";
   Regex ex = new Regex(pattern, RegexOptions.IgnoreCase);
   MatchCollection mc = ex.Matches(parmString);
   string[] paramNames = new string[mc.Count];
   int i = 0;
   foreach (Match m in mc)
   {
    paramNames[i] = m.Value;
    i++;
   }
   // now let&#39;s type the parameters
   int j = 0;
   Type t = null;
   foreach (object o in paramList)
   {
    t = o.GetType();
    SQLiteParameter parm = new SQLiteParameter();
    switch (t.ToString())
    {
     case ("DBNull"):
     case ("Char"):
     case ("SByte"):
     case ("UInt16"):
     case ("UInt32"):
     case ("UInt64"):
      throw new SystemException("Invalid data type");
 
     case ("System.String"):
      parm.DbType = DbType.String;
      parm.ParameterName = paramNames[j];
      parm.Value = (string)paramList[j];
      coll.Add(parm);
      break;
     case ("System.Byte[]"):
      parm.DbType = DbType.Binary;
      parm.ParameterName = paramNames[j];
      parm.Value = (byte[])paramList[j];
      coll.Add(parm);
      break;
     case ("System.Int32"):
      parm.DbType = DbType.Int32;
      parm.ParameterName = paramNames[j];
      parm.Value = (int)paramList[j];
      coll.Add(parm);
      break;
     case ("System.Boolean"):
      parm.DbType = DbType.Boolean;
      parm.ParameterName = paramNames[j];
      parm.Value = (bool)paramList[j];
      coll.Add(parm);
      break;
     case ("System.DateTime"):
      parm.DbType = DbType.DateTime;
      parm.ParameterName = paramNames[j];
      parm.Value = Convert.ToDateTime(paramList[j]);
      coll.Add(parm);
      break;
     case ("System.Double"):
      parm.DbType = DbType.Double;
      parm.ParameterName = paramNames[j];
      parm.Value = Convert.ToDouble(paramList[j]);
      coll.Add(parm);
      break;
     case ("System.Decimal"):
      parm.DbType = DbType.Decimal;
      parm.ParameterName = paramNames[j];
      parm.Value = Convert.ToDecimal(paramList[j]);
      break;
     case ("System.Guid"):
      parm.DbType = DbType.Guid;
      parm.ParameterName = paramNames[j];
      parm.Value = (System.Guid)(paramList[j]);
      break;
     case ("System.Object"):
      parm.DbType = DbType.Object;
      parm.ParameterName = paramNames[j];
      parm.Value = paramList[j];
      coll.Add(parm);
      break;
     default:
      throw new SystemException("Value is of unknown data type");
    } // end switch
    j++;
   }
   return coll;
  }
  /// <summary>
  /// Executes non query typed params from a DataRow
  /// </summary>
  /// <param name="command">Command.</param>
  /// <param name="dataRow">Data row.</param>
  /// <returns>Integer result code</returns>
  public static int ExecuteNonQueryTypedParams(IDbCommand command, DataRow dataRow)
  {
   int retVal = 0;
   // If the row has values, the store procedure parameters must be initialized
   if (dataRow != null && dataRow.ItemArray.Length > 0)
   {
    // Set the parameters values
    AssignParameterValues(command.Parameters, dataRow);
    retVal = ExecuteNonQuery(command);
   }
   else
   {
    retVal = ExecuteNonQuery(command);
   }
   return retVal;
  }
  /// <summary>
  /// This method assigns dataRow column values to an IDataParameterCollection
  /// </summary>
  /// <param name="commandParameters">The IDataParameterCollection to be assigned values</param>
  /// <param name="dataRow">The dataRow used to hold the command&#39;s parameter values</param>
  /// <exception cref="System.InvalidOperationException">Thrown if any of the parameter names are invalid.</exception>
  protected internal static void AssignParameterValues(IDataParameterCollection commandParameters, DataRow dataRow)
  {
   if (commandParameters == null || dataRow == null)
   {
    // Do nothing if we get no data
    return;
   }
   DataColumnCollection columns = dataRow.Table.Columns;
   int i = 0;
   // Set the parameters values
   foreach (IDataParameter commandParameter in commandParameters)
   {
    // Check the parameter name
    if (commandParameter.ParameterName == null ||
     commandParameter.ParameterName.Length <= 1)
     throw new InvalidOperationException(string.Format(
       "Please provide a valid parameter name on the parameter #{0},       the ParameterName property has the following value: &#39;{1}&#39;.",
      i, commandParameter.ParameterName));
    if (columns.Contains(commandParameter.ParameterName))
     commandParameter.Value = dataRow[commandParameter.ParameterName];
    else if (columns.Contains(commandParameter.ParameterName.Substring(1)))
     commandParameter.Value = dataRow[commandParameter.ParameterName.Substring(1)];
    i++;
   }
  }
  /// <summary>
  /// This method assigns dataRow column values to an array of IDataParameters
  /// </summary>
  /// <param name="commandParameters">Array of IDataParameters to be assigned values</param>
  /// <param name="dataRow">The dataRow used to hold the stored procedure&#39;s parameter values</param>
  /// <exception cref="System.InvalidOperationException">Thrown if any of the parameter names are invalid.</exception>
  protected void AssignParameterValues(IDataParameter[] commandParameters, DataRow dataRow)
  {
   if ((commandParameters == null) || (dataRow == null))
   {
    // Do nothing if we get no data
    return;
   }
   DataColumnCollection columns = dataRow.Table.Columns;
   int i = 0;
   // Set the parameters values
   foreach (IDataParameter commandParameter in commandParameters)
   {
    // Check the parameter name
    if (commandParameter.ParameterName == null ||
     commandParameter.ParameterName.Length <= 1)
     throw new InvalidOperationException(string.Format(
      "Please provide a valid parameter name on the parameter #{0}, the ParameterName property has the following value: &#39;{1}&#39;.",
      i, commandParameter.ParameterName));
    if (columns.Contains(commandParameter.ParameterName))
     commandParameter.Value = dataRow[commandParameter.ParameterName];
    else if (columns.Contains(commandParameter.ParameterName.Substring(1)))
     commandParameter.Value = dataRow[commandParameter.ParameterName.Substring(1)];
    i++;
   }
  }
  /// <summary>
  /// This method assigns an array of values to an array of IDataParameters
  /// </summary>
  /// <param name="commandParameters">Array of IDataParameters to be assigned values</param>
  /// <param name="parameterValues">Array of objects holding the values to be assigned</param>
  /// <exception cref="System.ArgumentException">Thrown if an incorrect number of parameters are passed.</exception>
  protected void AssignParameterValues(IDataParameter[] commandParameters, params object[] parameterValues)
  {
   if ((commandParameters == null) || (parameterValues == null))
   {
    // Do nothing if we get no data
    return;
   }
   // We must have the same number of values as we pave parameters to put them in
   if (commandParameters.Length != parameterValues.Length)
   {
    throw new ArgumentException("Parameter count does not match Parameter Value count.");
   }
   // Iterate through the IDataParameters, assigning the values from the corresponding position in the 
   // value array
   for (int i = 0, j = commandParameters.Length, k = 0; i < j; i++)
   {
    if (commandParameters[i].Direction != ParameterDirection.ReturnValue)
    {
     // If the current array value derives from IDataParameter, then assign its Value property
     if (parameterValues[k] is IDataParameter)
     {
      IDataParameter paramInstance;
      paramInstance = (IDataParameter)parameterValues[k];
      if (paramInstance.Direction == ParameterDirection.ReturnValue)
      {
       paramInstance = (IDataParameter)parameterValues[++k];
      }
      if (paramInstance.Value == null)
      {
       commandParameters[i].Value = DBNull.Value;
      }
      else
      {
       commandParameters[i].Value = paramInstance.Value;
      }
     }
     else if (parameterValues[k] == null)
     {
      commandParameters[i].Value = DBNull.Value;
     }
     else
     {
      commandParameters[i].Value = parameterValues[k];
     }
     k++;
    }
   }
  }
 }
}

Ich hoffe, dieser Artikel wird für die C#-Programmierung aller hilfreich sein.

Weitere C#-basierte Methoden für den Zugriff auf SQLite-Datenbanken basierend auf der SQLiteHelper-ähnlichen SqlHelper-Klasse und verwandte Artikel finden Sie auf der chinesischen PHP-Website!