DataRow is converted to generic, and the query data is directly converted to an object using reflection.

DataRow is converted to generic, and the query data is directly converted to an object using reflection.

Preface: This method converts DataRow into an object using reflection. Because reflection SetValue is said to be of poor performance, let's just look at it.

Using System; using System. collections. generic; using System. data; using System. linq; using System. reflection; using System. text; namespace WangSql. DBUtility {public class DataMapHelper {private enum ModelType {Value, String, Object, Reference} private static ModelType GetModelType (Type modelType) {if (modelType. isValueType) // value type {return ModelType. value;} else if (modelType = typeof (string) // reference type Special Type processing {return ModelType. string;} else if (modelType = typeof (object) // handle special types of reference {return ModelType. object;} else // reference type {return ModelType. reference ;}} public static List <T> DataTableToList <T> (DataTable table) {List <T> list = new List <T> (); foreach (DataRow item in table. rows) {list. add (DataRowToModel <T> (item);} return list;} public static T DataRowToModel <T> (DataRow row) {T model; Type type = typeof (T); ModelType modelType = GetModelType (type); switch (modelType) {case ModelType. value: // Value type {model = default (T); if (row [0]! = Null) model = (T) row [0];} break; case ModelType. string: // reference type c # string is also treated as value type {model = default (T); if (row [0]! = Null) model = (T) row [0];} break; case ModelType. object: // The reference type directly returns the value of the first column of the First row {model = default (T); if (row [0]! = Null) model = (T) row [0];} break; case ModelType. reference: // Reference type {model = System. activator. createInstance <T> (); // The reference type must be instantiated for the generic type # region MyRegion // obtain the attribute PropertyInfo [] modelPropertyInfos = type in the model. getProperties (); // traverse each attribute of the model and assign a value to the column foreach (PropertyInfo pi in modelPropertyInfos) corresponding to DataRow {// obtain the attribute name String name = pi. name; if (row. table. columns. contains (name) {// non-generic if (! Pi. propertyType. isGenericType) {if (pi. propertyType. isEnum) {pi. setValue (model, row [name], null);} else {pi. setValue (model, string. isNullOrEmpty (row [name]. toString ())? Null: Convert. changeType (row [name], pi. propertyType), null) ;}/// generic Nullable <> else {Type genericTypeDefinition = pi. propertyType. getGenericTypeDefinition (); // if (genericTypeDefinition = typeof (Nullable <>) can be null )) {// return the basic type parameter pi of the specified type that can be null. setValue (model, string. isNullOrEmpty (row [name]. toString ())? Null: Convert. changeType (row [name], Nullable. getUnderlyingType (pi. propertyType), null) ;}}# endregion} break; default: model = default (T); break;} return model ;}}}

 

After that,

1. You can use the cache to improve the performance.

After each typeof (T), store the object-related information (such as generic attributes) and read it from the cache the next time.

2. Improve SetValue.

You can assign values to generic delegates.

3. Use Emit