Question

我需要用c＃以编程方式创建两个表，这些表将有一些列，其中一个是on ID。 ID必须是一个从1开始的计数器，并且每行总是加1，并且该ID必须是第二个表上的外键。我该怎么做？我已经在互联网上搜索过，但没有找到最终结论。

Answer 1

您必须创建一个与另一个表B有关系的表A. 所以在表B中将是一个外键指向表A的ID的列。

表A

  ID          Column1     Column1  . . . 
   1          name1       value1
   2          nam2        value2

表B

  ID          Column1    Column2   table_A_id  . . . 
   1          name1      value1       1
   2          name2      value1       1
   3          name3      value1       2

Answer 2

public class DataStack1
{
    [System.ComponentModel.DataAnnotations.Key]
    public int id { get; set; }
    public string somedata { get; set; }
}
public class DataStack2
{
    [System.ComponentModel.DataAnnotations.Key]
    public int id { get; set; }
    public int DataStack1id { get; set; }
    public DataStack1 DataStack1 { get; set; }
    public string somedata { get; set; }
}

当您创建DBSets时，Entity Framework将识别此关系。要创建DBSets，请使用以下代码：

public class DataContext : DbContext
{
    public DbSet<DataStack1> DataStack1 { get; set; }
    public DbSet<DataStack2> DataStack2 { get; set; }
}

使用以下代码访问表格：

using (var dataset = new DataContext())
{
    var Data = dataset.DataStack1.ToList();
}

您可以将以下连接字符串添加到App.config文件中：

<connectionStrings>
<add name="DefaultConnection" connectionString="Data Source=(LocalDb)\MSSQLLocalDB;AttachDbFilename=|DataDirectory|\Data.mdf;Initial Catalog=Data-Project;Integrated Security=True" providerName="System.Data.SqlClient" />  </connectionStrings>

Answer 3

DataTable table1 =new DataTable();  
DataColumn autoIncrement=new DataColumn("AutoIncrement",typeof(System.Int32));   
table1.Columns.Add(autoIncrement);
autoIncrement.AutoIncrement=true;
autoIncrement.AutoIncrementSeed=1;
autoIncrement.ReadOnly =true;






DataTable dtEmployee = getEmployeeRecords();  
DataTable dtDepartment = getDepartmentRecords();  


DataColumn obj_ParentDepartmentID, obj_ChildDepartmentID;  
DataSet ds = new DataSet();
ds.Tables.Add(dtDepartment);
ds.Tables.Add(dtEmployee);
obj_ParentDepartmentID = ds.Tables["Department"].Columns["DeptID"];
obj_ChildDepartmentID = ds.Tables["Employee"].Columns["DeptID"];


dtEmployee.Columns.Add("DepartmentName");
DataRelation obj_DataRelation = new DataRelation("dept_reln", obj_ParentDepartmentID, obj_ChildDepartmentID);
ds.Relations.Add(obj_DataRelation);



foreach (DataRow dr_Employee in ds.Tables["Employee"].Rows)   
{

DataRow dr_Department = dr_Employee.GetParentRow(obj_DataRelation);     
dr_Employee["DepartmentName"] = dr_Department["DeptName"];    

}
DataTable dtResult = ds.Tables["Employee"].DefaultView.ToTable(false, "EmployeeID", "EmployeeName", "FatherName", "DepartmentName");

用id连接两个表

3 个答案: