近期开发项目中用到的编码小技巧汇总说明

Posted 2020-08-27

1.默认EF生成的连接字符串比较的长和怪异，若想使用普通的连接字符串来连接EF，则可以通过创建分部类，并重写一个构造函数，在构造函数中通过动态拼接EntityConnectionString得到EF所需的连接字符串，具代实现代码如下：

    public partial class DataEntities
    {
        private static ConcurrentDictionary<string, string> entityConnStrings = new ConcurrentDictionary<string, string>();

        public DataEntities(string connName)
            : base(BuildEntityConnectionString(connName))
        {

        }

        private static string BuildEntityConnectionString(string connName)
        {

            if (!entityConnStrings.ContainsKey(connName))
            {
                var connStrSetting = System.Configuration.ConfigurationManager.ConnectionStrings[connName];

                EntityConnectionStringBuilder entityConnStrBuilder = new EntityConnectionStringBuilder();
                entityConnStrBuilder.Provider = connStrSetting.ProviderName;
                entityConnStrBuilder.ProviderConnectionString = EncryptUtility.DesDecrypt("XXXXX", connStrSetting.ConnectionString);
                entityConnStrBuilder.Metadata = "res://*/Data.csdl|res://*/Data.ssdl|res://*/Data.msl";
                string entityConnString = entityConnStrBuilder.ToString();
                entityConnStrings.AddOrUpdate(connName, entityConnString, (key, value) => entityConnString);
            }
            return entityConnStrings[connName];
        }
    }

注意上面的类是一个分部类：partial，同时BuildEntityConnectionString方法是一个静态方法，在BuildEntityConnectionString方法中ProviderConnectionString = EncryptUtility.DesDecrypt("XXXXX", connStrSetting.ConnectionString);是关键，我这里是对config中的连接字符串 也都进行了加密，故此处我需要解密，若无这个需求可以直接：ProviderConnectionString =connStrSetting.ConnectionString即可。后续实例化EF上下文对象时，请使用：DataEntities(string connName)这个构造涵数即可，DataEntities是具体的EF上下文对象，大家的EF上下文类名均可能不相同。

2.支持一个通用对象的XML序列化（即：一个类中有可变类型属性成员，需要不同的序列结果及生成不同的序列元素名称），具体实现代码如下：

一个需要被序列化成XML的类：其中要求生成的XML元素detail必需有子元素，且子元素名称及子元素内部属性根据类型的不同而不同（即：detail元素下的子元素是可变的）

    [XmlRootAttribute("master")]
    public class DemoMaster<T> where T : class
    {
        [XmlElement("attr")]
        public string DemoAttr { get; set; }

        [XmlElement("detail")]
        public DemoDetail<T> DemoDetail { get; set; } //关键点在这里，该属性元素为：detail，但其子元素根据T不同而不同

    }
    public class DemoDetail<T> : IXmlSerializable where T : class
    {
        public T body { get; set; }

        public System.Xml.Schema.XmlSchema GetSchema()
        {
            return null;
        }

        public void ReadXml(System.Xml.XmlReader reader)
        {
            string bodyStr = reader.ReadInnerXml();
            this.body = XmlHelper.XmlDeserialize<T>(bodyStr, Encoding.UTF8);
        }

        public void WriteXml(System.Xml.XmlWriter writer)
        {
            writer.WriteRaw(XmlHelper.XmlSerialize(this.body, Encoding.UTF8, true));
        }
    }

    [XmlTypeAttribute("list-a", AnonymousType = false)]
    public class DemoDetailA
    {
        public string Apro1 { get; set; }

        public string Apro2 { get; set; }

        public string Apro3 { get; set; }
    }

    [XmlTypeAttribute("list-b", AnonymousType = false)]
    public class DemoDetailB
    {
        public string Bpro1 { get; set; }

        public string Bpro2 { get; set; }

        public string Bpro3 { get; set; }
    }

    [XmlTypeAttribute("list-c", AnonymousType = false)]
    public class DemoDetailC
    {
        public string Cpro1 { get; set; }

        public string Cpro2 { get; set; }

        public string Cpro3 { get; set; }
    }

注意上面代码中，需要关注：DemoDetail属性及DemoDetail<T>类，DemoDetail属性仅是为了生成detail元素节点，而子节点则由DemoDetail<T>类来进行生成，DemoDetail<T>是实现了IXmlSerializable接口，在XML序列化时，DemoDetail<T>类仅将body属性对应的T类型实例内容进行序列化（WriteRaw），而反序列化时，则先反序列化body属性对应的T类型实例，然后赋值给body属性，这也是巧妙之处，DemoDetail<T>类本身并没有真正参与到序列化中，故序列化的字符串也看不到DemoDetail<T>类相关的元素，DemoDetail<T>类仅仅是一个XML序列化格式生成的中介。序列化的XML结果如下：

序列化代码：

            var demo1 = new DemoMaster<DemoDetailA>()
            {
                DemoAttr = "demo1",
                DemoDetail = new DemoDetail<DemoDetailA>() { body = new DemoDetailA() { Apro1 = "demoA1", Apro2 = "demoA2", Apro3 = "demoA3" } }
            };

            var demo2 = new DemoMaster<DemoDetailB>()
            {
                DemoAttr = "demo2",
                DemoDetail = new DemoDetail<DemoDetailB>() { body = new DemoDetailB() { Bpro1 = "demoB1", Bpro2 = "demoB2", Bpro3 = "demoB3" } }
            };

            var demo3 = new DemoMaster<DemoDetailC>()
            {
                DemoAttr = "demo3",
                DemoDetail = new DemoDetail<DemoDetailC>() { body = new DemoDetailC() { Cpro1 = "demoC1", Cpro2 = "demoC2", Cpro3 = "demoC3" } }
            };

            textBox1.Text = XmlHelper.XmlSerialize(demo1, Encoding.UTF8);

            textBox1.Text += "\\r\\n" + XmlHelper.XmlSerialize(demo2, Encoding.UTF8);

            textBox1.Text += "\\r\\n" + XmlHelper.XmlSerialize(demo3, Encoding.UTF8);

序列化的XML:

<?xml version="1.0" encoding="utf-8"?>
<master>
    <attr>demo1</attr>
    <detail><list-a>
    <Apro1>demoA1</Apro1>
    <Apro2>demoA2</Apro2>
    <Apro3>demoA3</Apro3>
</list-a></detail>
</master>

<?xml version="1.0" encoding="utf-8"?>
<master>
    <attr>demo2</attr>
    <detail><list-b>
    <Bpro1>demoB1</Bpro1>
    <Bpro2>demoB2</Bpro2>
    <Bpro3>demoB3</Bpro3>
</list-b></detail>
</master>

<?xml version="1.0" encoding="utf-8"?>
<master>
    <attr>demo3</attr>
    <detail><list-c>
    <Cpro1>demoC1</Cpro1>
    <Cpro2>demoC2</Cpro2>
    <Cpro3>demoC3</Cpro3>
</list-c></detail>
</master>

3.winform DataGridView 实现指定列采取密码框模式显示与编辑，以及列绑定到复合属性（即：绑定到多层次属性），具体实现代码如下：

            dataGridView1.CellFormatting += new DataGridViewCellFormattingEventHandler(dataGridView1_CellFormatting);
            dataGridView1.EditingControlShowing += new DataGridViewEditingControlShowingEventHandler(dataGridView1_EditingControlShowing);


        public string EvaluateValue(object obj, string property)
        {
            string retValue = string.Empty;
            string[] names = property.Split(‘.‘);

            for (int i = 0; i < names.Count(); i++)
            {
                try
                {
                    var prop = obj.GetType().GetProperty(names[i]);
                    var result = prop.GetValue(obj, null);
                    if (result != null)
                    {
                        obj = result;
                        retValue = result.ToString();
                    }
                    else
                    {
                        break;
                    }
                }
                catch (Exception)
                {
                    throw;
                }
            }

            return retValue;
        }


        private void dataGridView1_CellFormatting(object sender, DataGridViewCellFormattingEventArgs e)
        {

            if (dataGridView1.Columns[e.ColumnIndex].DataPropertyName.Contains("."))
            {
                e.Value = EvaluateValue(dataGridView1.Rows[e.RowIndex].DataBoundItem, dataGridView1.Columns[e.ColumnIndex].DataPropertyName);
            }


            if (dataGridView1.Columns[e.ColumnIndex].Name == "KeyCode")
            {
                if (e.Value != null && e.Value.ToString().Length > 0)
                {
                    e.Value = new string(‘*‘, e.Value.ToString().Length);
                }
            }
        }

        private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
        {
            int i = this.dataGridView1.CurrentCell.ColumnIndex;
            bool usePassword = false;
            if (dataGridView1.Columns[i].Name == "KeyCode")
            {
                usePassword = true;
            }
            TextBox txt = e.Control as TextBox;
            if (txt != null)
            {
                txt.UseSystemPasswordChar = usePassword;
            }
        }

//示例：绑定的源数据类定义
    public class DemoBindClass
    {
        public string Attr { get; set; }

        public string KeyCode { get; set; }

        public DemoDetailA Detail { get; set; }
    }


    public class DemoDetailA
    {
        public string Apro1 { get; set; }

        public string Apro2 { get; set; }

        public string Apro3 { get; set; }

        public DemoDetailB DetailChild { get; set; }
    }


    public class DemoDetailB
    {
        public string Bpro1 { get; set; }

        public string Bpro2 { get; set; }

        public string Bpro3 { get; set; }
    }

绑定到数据源：

            var demo = new[] {
                new DemoBindClass()
                    {
                        Attr = "demo",
                        KeyCode="a123456789b",
                        Detail = new DemoDetailA()
                        {
                            Apro1 = "demoA1",
                            Apro2 = "demoA2",
                            Apro3 = "demoA3",
                            DetailChild = new DemoDetailB()
                            {
                                Bpro1 = "demoB1",
                                Bpro2 = "demoB2",
                                Bpro3 = "demoB3"
                            }
                        }
                    }
            };


            dataGridView1.AutoGenerateColumns = false;
            dataGridView1.DataSource = demo;

实现指定列采取密码框模式显示与编辑，以及列绑定到复合属性均需要订阅DataGridView的CellFormatting及EditingControlShowing事件，并在其中写转换当前Cell的Value，实现列绑定到复合属性，关键点在：EvaluateValue方法，该方法逻辑很简单，就是根据绑定的属性层级（.分隔）层层遍历获取属性的值，直到遍历完或为空时停止，最后得到的结果即是绑定的属性的值。最终实现的效果如下图示：