CreateCommand创建命令#region CreateCommand创建命令
/** <summary>
/// 创建一个由存储过程提供的命令
/// </summary>
/// <remarks>
/// e.g.:
/// SqlCommand command = CreateCommand(conn, "AddCustomer", "CustomerID", "CustomerName");
/// </remarks>
/// <param name="connection">一个合法的连接</param>
/// <param name="spName">存储过程名</param>
/// <param name="sourceColumns">源列名称数组</param>
/// <returns>一个合法的命令</returns>
internal static SqlCommand CreateCommand(SqlConnection connection, string spName, params string[] sourceColumns)
{
if (connection == null) throw new ArgumentException("connection");
if (spName == null || spName.Length == 0) throw new ArgumentException("spName");
//创建一个命令
SqlCommand cmd = new SqlCommand(spName, connection);
cmd.CommandType = CommandType.StoredProcedure;
//如果接受一个参数，则处理它
if ((sourceColumns != null) && (sourceColumns.Length > 0))
{
//提取存储过程参数
SqlParameter[] commandParameters = SqlHelperParameterCache.GetSpParameterSet(connection, spName);
//设置源列的名称
for (int index = 0; index < sourceColumns.Length; index++)
commandParameters[index].SourceColumn = sourceColumns[index];
//将参数附加到命令上
AttachParameters(cmd, commandParameters);
}
return cmd;
}
#endregion
/** <summary>
/// 这个方法将一个数组的值赋值到一个SqlParameter数组
/// </summary>
/// <param name="commandParameters">要被赋值的SqlParameter数组</param>
/// <param name="parameterValues">一个包含参数值的object数组</param>
private static void AssignParameterValues(SqlParameter[] commandParameters, object[] parameterValues)
{
if ((commandParameters == null) || parameterValues == null)
{
//如果没有数据则返回
return;
}
//参数的数量必须与值得数量匹配
if (commandParameters.Length != parameterValues.Length)
{
throw new ArgumentException("参数的个数不能匹配参数值的个数");
}
//迭代参数数组，把object数组的值赋给相应的参数
for (int i = 0, j = commandParameters.Length; i < j; i++)
{
//如果数组的值继承自IDbDataParameter,这是赋给它的属性值
if (parameterValues[i] is IDbDataParameter)
{
IDbDataParameter paraInstance = (IDbDataParameter)parameterValues[i];
if (paraInstance.Value == null)
{
commandParameters[i].Value = DBNull.Value;
}
else
{
commandParameters[i].Value = paraInstance.Value;
}
}
else if (parameterValues[i] == null)
{
commandParameters[i].Value = DBNull.Value;
}
else
{
commandParameters[i].Value = parameterValues[i];
}
}
}
//--上面的这个也不错，--其他的我也分析清楚了但是感觉一个晕为什么呢~~这个类的重载好多阿，- -不太喜欢故而不写出来- -
SqlHelperParameterCache- -一般就不要用了，浪费内存但是某些特殊情况不如，自动生成数据实体的时候- -瓦塞塞，好用级了，- -可以通过这家伙生成所有存储过程的实体，- -某些程序就是这么干的- -我们先来看看
/** <summary>
/// SqlHelperParameterCache 提供一些函数用来发现存储过程的参数
/// </summary>
internal sealed class SqlHelperParameterCache
{
private methods, variables, and constructors#region private methods, variables, and constructors
//这个类仅仅提供静态方法，并使用一个私有的构造器来阻止创建一个实例化对象
private SqlHelperParameterCache() { }
private static Hashtable paramCache = Hashtable.Synchronized(new Hashtable());
/** <summary>
/// 在运行时发现存储过程
/// </summary>
/// <param name="connection">一个合法的连接对象</param>
/// <param name="spName">存储过程名</param>
/// <param name="includeReturnValueParameter">是否包含返回的参数</param>
/// <returns>被发现的参数数组</returns>
private static SqlParameter[] DiscoverSpParameterSet(SqlConnection connection, string spName, bool includeReturnValueParameter)
{
if (connection == null) throw new ArgumentNullException("connection");
if (spName == null || spName.Length == 0) throw new ArgumentNullException("spName");
SqlCommand cmd = new SqlCommand(spName, connection);
cmd.CommandType = CommandType.StoredProcedure;
connection.Open();
SqlCommandBuilder.DeriveParameters(cmd);
connection.Close();
if (!includeReturnValueParameter)
{
cmd.Parameters.RemoveAt(0);
}
SqlParameter[] discoveredParameters = new SqlParameter[cmd.Parameters.Count];
cmd.Parameters.CopyTo(discoveredParameters, 0);
// 将参数置为DBNull.Value
foreach (SqlParameter discoveredParameter in discoveredParameters)
{
discoveredParameter.Value = DBNull.Value;
}
return discoveredParameters;
}
/** <summary>
/// 深度拷贝参数数组
/// </summary>
/// <param name="originalParameters"></param>
/// <returns></returns>
private static SqlParameter[] CloneParameters(SqlParameter[] originalParameters)
{
SqlParameter[] clonedParameters = new SqlParameter[originalParameters.Length];
for (int i = 0, j = originalParameters.Length; i < j; i++)
{
clonedParameters[i] = (SqlParameter)((ICloneable)originalParameters[i]).Clone();
}
return clonedParameters;
}
#endregion private methods, variables, and constructors
caching functions#region caching functions
/** <summary>
/// 将参数数组添加到缓存
/// </summary>
/// <param name="connectionString">一个合法的连接字符串</param>
/// <param name="commandText">命令文本</param>
/// <param name="commandParameters">被缓存的参数数组</param>
internal static void CacheParameterSet(string connectionString, string commandText, params SqlParameter[] commandParameters)
{
if (connectionString == null || connectionString.Length == 0) throw new ArgumentNullException("connectionString");
if (commandText == null || commandText.Length == 0) throw new ArgumentNullException("commandText");
string hashKey = connectionString + ":" + commandText;
paramCache[hashKey] = commandParameters;
}
/** <summary>
/// 从缓存中提取参数
/// </summary>
/// <param name="connectionString">一个合法的连接字符串</param>
/// <param name="commandText">命令文本</param>
/// <returns>参数数组</returns>
internal static SqlParameter[] GetCachedParameterSet(string connectionString, string commandText)
{
if (connectionString == null || connectionString.Length == 0) throw new ArgumentNullException("connectionString");
if (commandText == null || commandText.Length == 0) throw new ArgumentNullException("commandText");
string hashKey = connectionString + ":" + commandText;
SqlParameter[] cachedParameters = paramCache[hashKey] as SqlParameter[];
if (cachedParameters == null)
{
return null;
}
else
{
//为什么要进行克隆
return CloneParameters(cachedParameters);
}
}
#endregion caching functions
Parameter Discovery Functions#region Parameter Discovery Functions
/** <summary>
/// 获取存储过程的参数
/// </summary>
/// <remarks>
/// 这个方法将查询数据库，并将其放置在缓存中
/// </remarks>
/// <param name="connectionString">一个合法的连接</param>
/// <param name="spName">存储过程名</param>
/// <returns>数组参数</returns>
internal static SqlParameter[] GetSpParameterSet(string connectionString, string spName)
{
return GetSpParameterSet(connectionString, spName, false);
}
/** <summary>
/// 获取存储过程的参数
/// </summary>
/// <remarks>
/// 这个方法将查询数据库，并将其放置在缓存中
/// </remarks>
/// <param name="connectionString">一个合法的连接</param>
/// <param name="spName">存储过程名</param>
/// <param name="includeReturnValueParameter">是否在结果中返回参数值</param>
/// <returns>参数数组</returns>
internal static SqlParameter[] GetSpParameterSet(string connectionString, string spName, bool includeReturnValueParameter)
{
if (connectionString == null || connectionString.Length == 0) throw new ArgumentNullException("connectionString");
if (spName == null || spName.Length == 0) throw new ArgumentNullException("spName");
using (SqlConnection connection = new SqlConnection(connectionString))
{
return GetSpParameterSetInternal(connection, spName, includeReturnValueParameter);
}
}
/** <summary>
/// 获取存储过程的参数
/// </summary>
/// <remarks>
/// 这个方法将查询数据库，并将其放置在缓存中
/// </remarks>
/// <param name="connection">一个合法的连接对象</param>
/// <param name="spName">存储过程名</param>
/// <returns>参数数组</returns>
internal static SqlParameter[] GetSpParameterSet(SqlConnection connection, string spName)
{
return GetSpParameterSet(connection, spName, false);
}
/** <summary>
/// 获取存储过程的参数
/// </summary>
/// <remarks>
/// 这个方法将查询数据库，并将其放置在缓存中
/// </remarks>
/// <param name="connection">一个合法的连接对象</param>
/// <param name="spName">存储过程名</param>
/// <param name="includeReturnValueParameter">是否在结果中返回参数值</param>
/// <returns>参数数组</returns>
internal static SqlParameter[] GetSpParameterSet(SqlConnection connection, string spName, bool includeReturnValueParameter)
{
if (connection == null) throw new ArgumentNullException("connection");
using (SqlConnection clonedConnection = (SqlConnection)((ICloneable)connection).Clone())
{
return GetSpParameterSetInternal(clonedConnection, spName, includeReturnValueParameter);
}
}
/** <summary>
/// 这个方法将查询数据库，并将其放置在缓存中
/// </summary>
/// <param name="connection">一个合法的连接对象</param>
/// <param name="spName">存储过程名</param>
/// <param name="includeReturnValueParameter">是否在结果中返回参数值</param>
/// <returns>参数数组</returns>
private static SqlParameter[] GetSpParameterSetInternal(SqlConnection connection, string spName, bool includeReturnValueParameter)
{
if (connection == null) throw new ArgumentNullException("connection");
if (spName == null || spName.Length == 0) throw new ArgumentNullException("spName");
string hashKey = connection.ConnectionString + ":" + spName + (includeReturnValueParameter ? ":include ReturnValue Parameter" : "");
SqlParameter[] cachedParameters;
cachedParameters = paramCache[hashKey] as SqlParameter[];
if (cachedParameters == null)
{
SqlParameter[] spParameters = DiscoverSpParameterSet(connection, spName, includeReturnValueParameter);
paramCache[hashKey] = spParameters;
cachedParameters = spParameters;
}
return CloneParameters(cachedParameters);
}
#endregion Parameter Discovery Functions
}
