简单代码生成器原理剖析（二）
上篇《简单代码生成器原理剖析（一）》分析了代码生成器的原理，查询数据库系统视图：INFORMATION_SCHEMA.TABLES、 INFORMATION_SCHEMA.COLUMNS 可以获得数据库中表、列的相关信息，再运用StringBuilder类的其AppendLine方法追加字符串，最后早运用File.WriteAllText方法将字符串写入文件。
第二版代码生成器在第一版的基础上扩展了以下功能：
- 使用了部分类（partial）：当使用大项目或自动生成的代码（如由 Windows 窗体设计器提供的代码）时，将一个类、结构或接口类型拆分到多个文件中的做法就很有用。 分部类型可能包含分部方法。
- 使用可空类型：由于数据库中表中数据很有可能是NULL，可空类型使得数据从表中读取出来赋值给值类型更加兼容。
- 增加了ToModel方法：将数据库表中一行数据封装成Model类的对象返回。
Model的实现：
/// <summary>
/// Model
/// </summary>
public static void CreateModel(CodeBuilderArgs args,string tableName)
{
DataTable dt = ExecuteDataTable(args.ConnectionString, "select * from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME=@TABLE_NAME"
,new SqlParameter("TABLE_NAME",tableName));
StringBuilder sb = new StringBuilder();
sb.AppendLine("using System;");
sb.AppendLine("using System.Collections.Generic;");
sb.AppendLine("using System.Linq;");
sb.AppendLine("using System.Text;");
sb.AppendLine("namespace " + args .Namespace+ ".Model");
sb.AppendLine("{");
sb.AppendLine("partial class " + tableName);
sb.AppendLine("{");
foreach (DataRow row in dt.Rows)
{
string colName = Convert.ToString(row["COLUMN_NAME"]);
string colType = Convert.ToString(row["DATA_TYPE"]);
Type netType = GetTypeByDBType(colType);
string netTypeName;
if (netType.IsValueType)
{
netTypeName = netType + "?";
}
else
{
netTypeName = netType.ToString();
}
sb.AppendLine("public " +netTypeName +" "+ colName + " { get; set; }");
}
sb.AppendLine(" }");
sb.AppendLine(" }");
string modelDir = Path.Combine(args.OutputDir, "Model");
string modelFile = Path.Combine(modelDir, tableName+".cs");
Directory.CreateDirectory(modelDir);
File.WriteAllText(modelFile, sb.ToString());
}DAL（数据访问层）的实现：
/// <summary>
///DAL
/// </summary>
/// <param name="args"></param>
/// <param name="tableName"></param>
public static void CreateDAL(CodeBuilderArgs args, string tableName)
{
StringBuilder sb = new StringBuilder();
DataTable dt = ExecuteDataTable(args.ConnectionString, "select * from INFORMATION_SCHEMA.COLUMNS where TABLE_NAME=@TABLE_NAME"
, new SqlParameter("TABLE_NAME", tableName));
sb.AppendLine("using System;");
sb.AppendLine("using System.Collections.Generic;");
sb.AppendLine("using System.Linq;");
sb.AppendLine("using System.Text;");
sb.AppendLine("using "+args.Namespace+".Model;");
sb.AppendLine("using System.Data.SqlClient;");
sb.AppendLine("using System.Data;");
sb.AppendLine("namespace "+args.Namespace+".DAL");
sb.AppendLine("{");
sb.AppendLine("partial class "+tableName+"DAL");
sb.AppendLine("{");
sb.AppendLine("public int AddNew("+tableName+" model)");
sb.AppendLine("{");
string[] cols = GetColsWithoutId(GetCols(dt, new List<string>())).ToArray();
var colsParameters=from e in cols select"@"+ e;
sb.AppendLine("string sql = \"insert into " + tableName + "(" + string.Join(",", cols) + ") output inserted.id values(" + string.Join(",", colsParameters.ToArray()) + ")\";");
sb.AppendLine("int id = (int)SqlHelper.ExecuteScalar(sql");
foreach (DataRow row in dt.Rows)
{
string colName = Convert.ToString(row["COLUMN_NAME"]);
if(!(colName.ToLower()=="id"))
{
sb.AppendLine(", new SqlParameter(\""+colName+"\", model."+colName+")");
}
}
sb.AppendLine(");");
sb.AppendLine("return id;");
sb.AppendLine("}");
var par=from e in cols select e+"="+"@"+e;
sb.AppendLine("public bool Update("+tableName+" model)");
sb.AppendLine("{");
sb.AppendLine("string sql = \"update "+tableName+" set "+string.Join(",",par.ToArray())+" where id=@id\";");
sb.AppendLine("int rows = SqlHelper.ExecuteNonQuery(sql");
foreach (DataRow row in dt.Rows)
{
string colName = Convert.ToString(row["COLUMN_NAME"]);
sb.AppendLine(", new SqlParameter(\"" + colName + "\", model." + colName + ")");
}
sb.AppendLine(");");
sb.AppendLine("return rows>0;");
sb.AppendLine("}");
sb.AppendLine("public bool Delete(int id)");
sb.AppendLine("{");
sb.AppendLine("int rows = SqlHelper.ExecuteNonQuery(\"delete from "+tableName+" where id=@id\",");
sb.AppendLine("new SqlParameter(\"id\", id));");
sb.AppendLine("return rows > 0;");
sb.AppendLine("}");
sb.AppendLine("private static "+tableName+" ToModel(DataRow row)");
sb.AppendLine("{");
sb.AppendLine(""+tableName+" model = new "+tableName+"();");
foreach (DataRow row in dt.Rows)
{
string colName = Convert.ToString(row["COLUMN_NAME"]);
string colType = Convert.ToString(row["DATA_TYPE"]);
Type netType = GetTypeByDBType(colType);
string netTypeName;
if (netType.IsValueType)
{
netTypeName = netType + "?";
}
else
{
netTypeName = netType.ToString();
}
sb.AppendLine("model."+colName+" = row.IsNull(\""+colName+"\") ? null : "+"("+netTypeName+")"+"row[\""+colName+"\"];");
}
sb.AppendLine("return model;");
sb.AppendLine("}");
//
sb.AppendLine("public "+tableName+" Get(int id)");
sb.AppendLine("{");
sb.AppendLine("DataTable dt = SqlHelper.ExecuteDataTable(\"select * from "+tableName+" where id=@id\",");
sb.AppendLine("new SqlParameter(\"id\", id));");
sb.AppendLine("if(dt.Rows.Count > 1)");
sb.AppendLine("{");
sb.AppendLine("throw new Exception(\"more than 1 row was found\");");
sb.AppendLine("}");
sb.AppendLine("if(dt.Rows.Count <= 0)");
sb.AppendLine("{");
sb.AppendLine("return null; ");
sb.AppendLine("}");
sb.AppendLine("DataRow row = dt.Rows[0];");
sb.AppendLine(""+tableName+" model = ToModel(row);");
sb.AppendLine("return model;");
sb.AppendLine("}");
sb.AppendLine("public IEnumerable<"+tableName+">ListAll()");
sb.AppendLine("{");
sb.AppendLine("List<"+tableName+"> list = new List<"+tableName+">();");
sb.AppendLine("DataTable dt = SqlHelper.ExecuteDataTable(\"select * from "+tableName+"\");");
sb.AppendLine("foreach (DataRow row in dt.Rows)");
sb.AppendLine("{");
sb.AppendLine("list.Add(ToModel(row));");
sb.AppendLine("}");
sb.AppendLine("return list;");
sb.AppendLine("}");
sb.AppendLine("}");
sb.AppendLine("}");
string DALlDir = Path.Combine(args.OutputDir,"DAL");
string DALFile = Path.Combine(DALlDir,tableName+"DAL.cs");
Directory.CreateDirectory(DALlDir);
File.WriteAllText(DALFile,sb.ToString());
}
private static IEnumerable<string> GetColsWithoutId(List<string> cols)
{
var colArray = from col in cols where col.ToLower() != "id" select col;
return colArray;
}
private static List<string> GetCols(DataTable dt, List<string> cols)
{
foreach (DataRow row in dt.Rows)
{
string colName = Convert.ToString(row["COLUMN_NAME"]);
cols.Add(colName);
}
return cols;
}BLL的实现：
/// <summary>
/// BLL
/// </summary>
/// <param name="args"></param>
/// <param name="tableName"></param>
public static void CreateBLL(CodeBuilderArgs args,string tableName)
{
StringBuilder sb = new StringBuilder();
sb.AppendLine("using System;");
sb.AppendLine("using System.Collections.Generic;");
sb.AppendLine("using System.Linq;");
sb.AppendLine("using System.Text;");
sb.AppendLine("using "+args.Namespace+".Model;");
sb.AppendLine("using "+args.Namespace+".DAL;");
sb.AppendLine("namespace "+args.Namespace+".BLL");
sb.AppendLine("{");
sb.AppendLine("partial class "+tableName+"BLL");
sb.AppendLine("{");
sb.AppendLine("public int AddNew("+tableName+" model)");
sb.AppendLine("{");
sb.AppendLine("return new "+tableName+"DAL().AddNew(model);");
sb.AppendLine("}");
sb.AppendLine("public bool Delete(int id)");
sb.AppendLine("{");
sb.AppendLine("return new "+tableName+"DAL().Delete(id);");
sb.AppendLine("}");
sb.AppendLine("public bool Update("+tableName+" model)");
sb.AppendLine("{");
sb.AppendLine("return new "+tableName+"DAL().Update(model);");
sb.AppendLine("}");
sb.AppendLine("public "+tableName+" Get(int id)");
sb.AppendLine("{");
sb.AppendLine("return new "+tableName+"DAL().Get(id);");
sb.AppendLine("}");
sb.AppendLine("public IEnumerable<"+tableName+"> ListAll()");
sb.AppendLine("{");
sb.AppendLine("return new "+tableName+"DAL().ListAll();");
sb.AppendLine("}");
sb.AppendLine("}");
sb.AppendLine("}");
string BLLDir = Path.Combine(args.OutputDir,"BLL");
string BLLFile = Path.Combine(BLLDir,tableName+"BLL.cs");
Directory.CreateDirectory(BLLDir);
File.WriteAllText(BLLFile,sb.ToString());
}详细代码可参考：
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原始发表：2012-03-08 ，如有侵权请联系 cloudcommunity@tencent.com 删除
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