随手写的一个对DataRow和DataSqlReader的扩展方法
因为觉得一般使用DataRow获取行数据时使用字符串 会有太多的不确定和类型判断所以想自己扩展一下
最后成果
public class Model { public int objUserID { get; set; } public string FirstName { get; set; } } class Program { static void Main(string[] args) { DataRow r = null; var contact= r.GetContact<Model>();//声明一个DataRow的链接 //获取值类型 var id=contact.GetValue(s => s.objUserID,s=>int.Parse(s)); //获取引用类型 var name = contact.GetClassValue(s => s.FirstName); //直接获取int类型 id = contact.GetValueByDBNull(s => s.objUserID); System.Data.SqlClient.SqlDataReader reader = null; contact = reader.GetContact<Model>();//声明一个SqlDataReader的链接 //获取值类型 id = contact.GetValue(s => s.objUserID); //直接获取int类型 id = contact.GetValueByDBNull(s => s.objUserID); } }
开始定义一部分接口,公开外部可访问的方法
public interface ContactBase<T> { /// <summary> /// 获取值类型 /// </summary> TResult GetValue<TResult>(System.Linq.Expressions.Expression<Func<T, TResult>> exp, Func<string, TResult> convert=null); /// <summary> /// 获取引用类型 /// </summary> TResult GetClassValue<TResult>(System.Linq.Expressions.Expression<Func<T, TResult>> exp,Func<object,TResult> convert=null) where TResult :class; /*获取指定类型*/ int GetValueByDBNull(System.Linq.Expressions.Expression<Func<T, int>> exp); int GetValueByDBNull(System.Linq.Expressions.Expression<Func<T, double>> exp); int GetValueByDBNull(System.Linq.Expressions.Expression<Func<T, string>> exp); }
然后写根据接口定义的抽象类,里面写一些工具方法和公共属性
public abstract class ContactTools<T,TData>:ContactBase<T> { /// <summary> /// 存放row或reader的值 /// </summary> private TData _data; protected ContactTools(TData data) { this._data = data; } /// <summary> /// 通过lambda获取row或reader值 /// </summary> private object GetDBValue<TResult>(System.Linq.Expressions.Expression<Func<T, TResult>> exp, Func<string, object> getFunc) { if (exp == null || getFunc == null) return default(TResult); var member = exp.Body as System.Linq.Expressions.MemberExpression; var name = member.Member.Name; return getFunc(name); } /// <summary> /// 需要继承的改变 /// </summary> public abstract virtual object GetData(TData data,string name); public TResult GetValue<TResult>(System.Linq.Expressions.Expression<Func<T, TResult>> exp, Func<string, TResult> convert = null) { var value = this.GetDBValue(exp,s=>this.GetData(this._data,s)); if (value == DBNull.Value) return default(TResult); if (string.IsNullOrEmpty(value.ToString())) return default(TResult); if (convert == null) return (TResult)value; else return convert(value.ToString()); } public TResult GetClassValue<TResult>(System.Linq.Expressions.Expression<Func<T, TResult>> exp, Func<object, TResult> convert = null) where TResult : class { var value = this.GetDBValue(exp, s => this.GetData(this._data, s)); if (value == DBNull.Value) return null; if (convert == null) return value as TResult; else return convert(value); } public int GetValueByDBNull(System.Linq.Expressions.Expression<Func<T, int>> exp) { return this.GetValue(exp, s => int.Parse(s)); } public double GetValueByDBNull(System.Linq.Expressions.Expression<Func<T, double>> exp) { return this.GetValue(exp, s => double.Parse(s)); } public string GetValueByDBNull(System.Linq.Expressions.Expression<Func<T, string>> exp) { var str =this.GetClassValue(exp); return str == null ? string.Empty : str; } }
public class DataRowContact<T> : ContactTools<T, DataRow> { public DataRowContact(DataRow row):base(row){} public override object GetData(DataRow data, string name) { return data[name]; } }
实现DataSqlReader
public class DataReaderContact<T> : ContactTools<T, System.Data.SqlClient.SqlDataReader> { public DataReaderContact(System.Data.SqlClient.SqlDataReader reader) : base(reader) { } public override object GetData(System.Data.SqlClient.SqlDataReader data, string name) { return data[name]; } }
最后写扩展方法,扩展到DataRow和DataSqlReader中
public static class MyLinq { public static ContactBase<T> GetContact<T>(this DataRow row) { return new DataRowContact<T>(row); } public static ContactBase<T> GetContact<T>(this System.Data.SqlClient.SqlDataReader reader) { return new DataReaderContact<T>(reader); } }
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