如何封装存储过程调用

Question

我有一个用来做数据库操作的DAO类。我有很多从不同方法/函数调用的存储过程。在每个函数/方法中，我都编写了一行代码来为SP添加参数值。有没有什么方法可以封装它，这样所有的函数/方法都可以调用这个封装的功能来将参数传递给不同的存储过程。我相信你们中的许多人都做过类似的事情。基本上，我试图避免多余的语句来将参数添加到参数集合中。

(我使用的是C# 3.5)

Answer 1

可能是这样的：

public static IDataReader GetDataReader(string connectionStringKey, string storedProcedure, Dictionary<string, object> parameters) {
    try {
        SqlCommand command = GetCommandWithConnection(connectionStringKey);
        command.CommandText = storedProcedure;
        command.CommandType = CommandType.StoredProcedure;
        foreach (var parameter in parameters ?? new Dictionary<string, object>())
            command.Parameters.AddWithValue(parameter.Key, parameter.Value);
        command.Connection.Open();
        return command.ExecuteReader();
    }
    catch (Exception e) {
        Log.Error(string.Format("Error in GetDataReader, executing sp: {0}", storedProcedure), e);
        throw;
    }     
}
private static SqlCommand GetCommandWithConnection(string connectionStringKey) {
    return new SqlConnection(GetConnectionString(connectionStringKey)).CreateCommand();
}
private static string GetConnectionString(string connectionStringKey) {
    return ConfigurationManager.ConnectionStrings[connectionStringKey].ToString();
}

Edit:因为你已经添加了注释来说明你需要支持输出参数，下面是来自同一个dal类的另一个方法：

public static T GetScalar<T>(string connectionStringKey, string storedProcedure, Parameters parameters) {
    try {
        List<Parameter> outs = null;
        SqlCommand command = GetCommandWithConnection(connectionStringKey);
        command.CommandText = storedProcedure;
        command.CommandType = CommandType.StoredProcedure;
        if (parameters != null) {
            outs = parameters.FindAll(p => p.Direction != ParameterDirection.Input);
            parameters.ForEach(p => command.Parameters.AddWithValue(p.Key, p.Value).Direction = p.Direction);
        }
        command.Connection.Open();
        object o = command.ExecuteScalar();
        T result = (o != null) ? (T)o : default(T);
        if (outs != null && outs.Count > 0) {
            foreach (Parameter parameter in outs) {
                SqlParameter sqlParameter = command.Parameters[parameter.Key];
                parameters[parameter.Key] = (sqlParameter.Value == DBNull.Value) ? null : sqlParameter.Value;
            }
        }
        command.Connection.Close();
        if (o == null && (typeof(T) == typeof(int)) && parameters != null && parameters.ContainsKey("RowCount"))
            result = (T)parameters["RowCount"];
        return result;
    }
    catch (Exception e) {
        Log.Error(String.Format("Error in GetScalar<{0}>, executing sp: {1}", typeof(T).Name, storedProcedure), e);
        throw;
    }
}

和支持的参数类：

public class Parameter{
    public string Key { get; private set; }
    public object Value { get; protected internal set; }
    public ParameterDirection Direction { get; protected internal set; }
    public Parameter(string key, object value) : this(key, value, ParameterDirection.Input) { }
    public Parameter(string key, object value, ParameterDirection direction){
        Key = key;
        Value = value;
        Direction = direction;
    }
}
public class Parameters : List<Parameter>{
    public Parameters() { }
    public Parameters(object o){
        Populate(o);
    }
    public void Add(string key, object value){
        if (ContainsKey(key))
            throw new Exception("Parameter with the specified key already exists.");
        Add(new Parameter(key, value));
    }
    public void Add(string key, object value, ParameterDirection direction){
        if (ContainsKey(key))
            throw new Exception("Parameter with the specified key already exists.");
        Add(new Parameter(key, value, direction));
    }
    public bool ContainsKey(string key){
        return (Find(p => p.Key == key) != null);
    }
    protected internal int GetIndex(string key){
        int? index = null;
        for (int i = 0; i < Count; i++){
            if (this[i].Key == key){
                index = i;
                break;
            }
        }
        if (index == null)
            throw new IndexOutOfRangeException("Parameter with the specified key does not exist.");
        return (int)index;
    }
    public object this[string key]{
        get { return this[GetIndex(key)].Value; }
        set { this[GetIndex(key)].Value = value; }
    }
    private void Populate<T>(T obj){
        foreach (KeyValuePair<string, object> pair in new ObjectProperties(obj, BindingFlags.Public | BindingFlags.Instance))
            Add(pair.Key, pair.Value);
    }
}