Question

我的VSTO插件中有三个/四个函数和一些成员变量：

会员变量：

private Dictionary<string, string> clientDict;
private Dictionary<string, string> clientHistoryDict;

适用于这些变量的函数：

public void generateClientDict()
{
        clientDict.Add("alcatel-lucent.com", "Alcatel-Lucent");
        clientDict.Add("emerson.com", "Emerson");
        clientDict.Add("ericsson.com", "Ericsson");
        clientDict.Add("fortress-technologies.com", "Fortress Technologies");
        clientDict.Add("genesys.com", "Genesys");
        clientDict.Add("hitachi.com", "Hitachi Data Systems");
        clientDict.Add("hp.com", "Hewlett Packard");
        clientDict.Add("lg.com", "LG Electronics"); 
        clientDict.Add("samsung.com", "Samsung");
        clientDict.Add("sap.com", "SAP");
        clientDict.Add("tellabs.com", "Tellabs");
        clientDict.Add("thiel-audio.com", "Thiel Audio");
        clientDict.Add("xerox.com", "Xerox");
        clientDict.Add("zebra.com", "Zebra Technologies");

        clientHistoryDict.Add("3com.com", "3Com- CommWorks");
        clientHistoryDict.Add("3m.com", "3M");
        clientHistoryDict.Add("abis.com", "ABIS");
        clientHistoryDict.Add("acxiom.com", "Acxiom");
        clientHistoryDict.Add("ajusa.com", "AJ-USA");
        clientHistoryDict.Add("akamai.com", "Akamai Technologies");
        clientHistoryDict.Add("alcatel-lucent.com", "Alcatel-Lucent");
        clientHistoryDict.Add("avaya.com", "Avaya");
        clientHistoryDict.Add("beckmancoulter.com", "Beckman Coulter");
        clientHistoryDict.Add("bellsouth.com", "BellSouth");
        clientHistoryDict.Add("bridgevine.com", "Bridgevine");
        clientHistoryDict.Add("casio.com", "Casio");
        clientHistoryDict.Add("cca.com", "CCA");
        clientHistoryDict.Add("ccs.com", "CCS");
        clientHistoryDict.Add("centurylink.com", "CenturyLink");
        clientHistoryDict.Add("chinatelecom.com", "China Telecom");
        clientHistoryDict.Add("cisco.com", "Cisco");
        clientHistoryDict.Add("comcast.com", "Comcast");
        clientHistoryDict.Add("comodo.com", "Comodo");
        clientHistoryDict.Add("comverge.com", "Comverge");
        clientHistoryDict.Add("coriant.com", "Coriant (Spin off from Tellabs)");
        clientHistoryDict.Add("daneelectric.com", "Dane Electric");
        clientHistoryDict.Add("dell.com", "Dell");
        clientHistoryDict.Add("disney.com", "Disney");
        clientHistoryDict.Add("siemens.com", "Efficient Networks- Siemens");
        clientHistoryDict.Add("emc.com", "EMC");
        clientHistoryDict.Add("emergentcommunications.com", "Emergent Communications");
        clientHistoryDict.Add("emerson.com", "Emerson");
        clientHistoryDict.Add("epson.com", "Epson");
        clientHistoryDict.Add("ericsson.com", "Ericsson");
        clientHistoryDict.Add("exigen.com", "Exigen Services");
        clientHistoryDict.Add("frbny.com", "Federal Reverse Bank of New York");
        clientHistoryDict.Add("hometeamsports.com", "Fox Home Team Sports");
        clientHistoryDict.Add("freemansoundlabs.com", "Freeman Sound Labs");
        clientHistoryDict.Add("genesys.com", "Genesys");
        clientHistoryDict.Add("here.com", "HERE, a Nokia Company");
        clientHistoryDict.Add("hp.com", "Hewlett Packard");
        clientHistoryDict.Add("hitachi.com", "Hitachi Data Systems");
        clientHistoryDict.Add("intel.com", "Intel");
        clientHistoryDict.Add("lg.com", "LG Electronics");
        clientHistoryDict.Add("samsung.com", "Samsung");
        clientHistoryDict.Add("sap.com", "SAP");
        clientHistoryDict.Add("subway.com", "Subway");
        clientHistoryDict.Add("tellabs.com", "Tellabs");
        clientHistoryDict.Add("thiel-audio.com", "Thiel Audio");
        clientHistoryDict.Add("xerox.com", "Xerox");
        clientHistoryDict.Add("zebra.com", "Zebra Technologies");
}

现在这个函数适用于成员变量。（所有这些都属于同一类）。但这些功能不会：

public void populateClientDict(SqlConnection conn)
{
        //Dictionary<string, string> clientDict = new Dictionary<string, string>();  If I don't add this I get an error
        try
        {
            using (conn)
            {
                SqlCommand command = new SqlCommand(
                  @"SELECT ClientDirName, ClientEmailDomain FROM ClientTable;",
                  conn);
                conn.Open();

                SqlDataReader reader = command.ExecuteReader();

                if (reader.HasRows)
                {
                    while (reader.Read())
                    {
                        string clientDir = reader.GetString(0);
                        string clientEmail = reader.GetString(1);
                        clientDict.Add(clientEmail, clientDir);
                    }
                }
                else
                {
                    MessageBox.Show("No rows found in ClientTable", "Rows Not Found", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
                reader.Close();
            }
        }
        catch (InvalidOperationException ex)
        {
            MessageBox.Show(String.Format("Exception while accessing ClientTable: {0}", ex), "Exception", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
        catch (SqlException ex)
        {
            MessageBox.Show(String.Format("Exception while accessing ClientTable: {0}", ex), "Exception", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
}

public void populateClientHistoryDict(SqlConnection conn)
{
        //Dictionary<string, string> clientHistoryDict = new Dictionary<string, string>(); if I don't add this I get an error
        try
        {
            using (conn)
            {
                SqlCommand command = new SqlCommand(
                  @"SELECT ClientDirName, ClientEmailDomain FROM ClientHistoryTable;",
                  conn);
                conn.Open();

                SqlDataReader reader = command.ExecuteReader();

                if (reader.HasRows)
                {
                    while (reader.Read())
                    {
                        string clientDir = reader.GetString(0);
                        string clientEmail = reader.GetString(1);
                        clientHistoryDict.Add(clientEmail, clientDir);
                    }
                }
                else
                {
                    MessageBox.Show("No rows found in ClientHistoryTable", "Rows Not Found", MessageBoxButtons.OK, MessageBoxIcon.Error);
                }
                reader.Close();
            }
        }
        catch (InvalidOperationException ex)
        {
            MessageBox.Show(String.Format("Exception while accessing ClientHistoryTable: {0}", ex), "Exception", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
        catch (SqlException ex)
        {
            MessageBox.Show(String.Format("Exception while accessing ClientHistoryTable: {0}", ex), "Exception", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
}

正如我在函数中注释掉的那一行中写的，除非我在这些函数中声明字典，否则我会收到此错误：

我在这一行得到错误：

populateClientHict（）中的

clientDict.Add(clientEmail, clientDir);和populateClientHistoryDict（）中的clientHistoryDict.Add(clientEmail, clientDir);

An exception of type 'System.NullReferenceException' occurred in Archive.dll but was not handled in user code

Additional information: Object reference not set to an instance of an object.

我有一种感觉，错误与这部分功能有关：

while (reader.Read())
{
clientDir = reader.GetString(0);
string clientEmail = reader.GetString(1);
clientDict.Add(clientEmail, clientDir);
}

ID是第一列，clientDir是第二列，clientEmail是第三列。也许我错误地使用了reader.GetString()？我在某处读到了reader.GetString["ClientDirName"]之类的东西（ClientDirName是列名），但我不确定要做的是什么。

这会导致错误吗？如果是这样，我如何正确访问第2列和第3列（提供的ID是第一列）以避免此错误。

如果没有，还有什么可能导致它？

我已经尝试了大量的组合，正如我所说，如果我在函数中移动字典实例，但我不认为这解决了实际问题。

非常感谢任何帮助。

Answer 1

我猜你忘记了instantiate clientDict成员variable，就像你function中那样。

由于您在function中声明了相同的变量并进行实例化，因此它采用了本地范围（在没有this的情况下使用时）并且它可以正常工作。

您可以在constructor或declaration内部实例化您的私人会员。

private Dictionary<string, string> clientDict=new Dictionary<string, string>();
private Dictionary<string, string> clientHistoryDict=new Dictionary<string, string>();

如果您想了解有关范围的更多信息，请点击this链接。

C＃成员变量范围

1 个答案: