c# - 将参数从 DbCommand 复制到另一个 DbCommand

Question

你如何将DbCommand参数复制到另一个DbCommand，我想要一个DbCommand与我上次相同的参数的新的DbCommand。但现在使用不同的 sql 字符串。

Answer 1

// Copy parameters from cmd1 to cmd2
// Creates an array with new parameters
var nsp = cmd1.Parameters.Cast<ICloneable>().Select(x => x.Clone() as SqlParameter).Where(x => x != null).ToArray();
// Copy parameters into another command
cmd2.Parameters.AddRange(nsp);

Answer 2

您可以将需要重用的代码放在单独的方法中：

public DbCommand RecycledParameters(string sql, IList<DbParameter> parameters)
{
    var result = db.GetSqlStringCommand(sql);
    foreach(DbParameter p in parameters)
    {  
        db.AddInParameter(result, p.ParameterName, p.DbType, p.Value);
    }
    return result;
}

Answer 3

你能做这样的事情吗？

  System.Data.Common.DbCommand command = new System.Data.SqlClient.SqlCommand();
  System.Data.Common.DbCommand command1 = new System.Data.SqlClient.SqlCommand();

  command1.Parameters.AddRange(command.Parameters.Cast<System.Data.Common.DbParameter>().ToArray());

Answer 4

如果您所追求的只是 parms 集合，您可以尝试一种帮助方法，该方法在您的命令上创建 .parameters 集合的深层副本。看看这是否会吐出你要找的东西。

我不能将 ObjectCopier 方法归功于它，它只是我从过去的项目中获得的一个有用的基类方法。

    private DbParameterCollection cloneParms(DbCommand commandWithParms)
    {
        return ObjectCopier.Clone<DbParameterCollection>(commandWithParms.Parameters);
    }

    public static class ObjectCopier
    {
        /// <summary>
        /// Perform a deep Copy of the object.
        /// </summary>
        /// <typeparam name="T">The type of object being copied.</typeparam>
        /// <param name="source">The object instance to copy.</param>
        /// <returns>The copied object.</returns>
        public static T Clone<T>(T source)
        {
            if (!typeof(T).IsSerializable)
            {
                throw new ArgumentException("The type must be serializable.", "source");
            }

            // Don't serialize a null object, simply return the default for that object
            if (Object.ReferenceEquals(source, null))
            {
                return default(T);
            }

            IFormatter formatter = new BinaryFormatter();
            Stream stream = new MemoryStream();
            using (stream)
            {
                formatter.Serialize(stream, source);
                stream.Seek(0, SeekOrigin.Begin);
                return (T)formatter.Deserialize(stream);
            }
        }
    }   

Answer 5

vb.net中的一个简单方法

p 是传入的 sql 参数：

Dim p1 As SqlClient.SqlParameter = CType(CType(p, ICloneable).Clone, SqlClient.SqlParameter)

Answer 6

private List<Tuple<string, SqlDbType, string>> where_param;
public IEnumerable<SqlParameter> RecycledParameters(){
  foreach(Tuple<string, SqlDbType, string> tuple in where_param) {
    SqlParameter local_arg = new SqlParameter(tuple.Item1, tuple.Item2);
    local_arg.Value = tuple.Item3;
    yield return local_arg;
  }
}