C# 如何使用select from表中的字符串？

如何使用select from表中的字符串？ 例如：

private void Select(string strKind,int Rank, string Blah)
        {
            var strWhere ="";
            if(strKind == "RANK")
            {
                strWhere  = "where P.IDRANK ==" + Rank;
            }
            else 
            {
                strWhere  = "where P.IDRANK == " + Rank + " && P.BLAH == " + Blah;
            }

            DBEntities MyDB = new DBEntities();
            var Query1 = from P in MyDB.Per
                            strWhere 
                         select P;
        }

转换此查询：

 DBEntities MyDB = new DBEntities();
        var Query1 = from P in MyDB.Per
        where P.IDRANK == 2
        select P;
to:


 string strquery = "where P.IDRANK == 2";
    DBEntities MyDB = new DBEntities();
    var Query1 = from P in MyDB.Per
         strquery 
    select P;

private void Select(string strKind,int Rank, string Blah)
        {
            var strWhere ="";
            if(strKind == "RANK")
            {
                strWhere  = "where P.IDRANK ==" + Rank;
            }
            else 
            {
                strWhere  = "where P.IDRANK == " + Rank + " && P.BLAH == " + Blah;
            }

            DBEntities MyDB = new DBEntities();
            var Query1 = from P in MyDB.Per
                            strWhere 
                         select P;
        }

---

如果您可以获得一个DataTable，下面是您如何做到这一点的：

// Build a data table and add columns
DataTable dt = new DataTable();
dt.Columns.Add("IDRank");
dt.Columns.Add("Blah");

// Add rows to the table
for (int i = 1; i < 5; i++) {
    DataRow dr = dt.NewRow();
    dr["IDRank"] = i;
    dr["Blah"] = "Blah" + i.ToString();
    dt.Rows.Add(dr);
}           

// Get a DataView to table
DataView dv = dt.AsDataView();

// Define the filter
string filter = "IDRank = 2";

// Apply the filter
dv.RowFilter = filter;

// Run the query
var Query1 = from P in dv.ToTable().AsEnumerable() select P;

private void Select(string strKind,int Rank, string Blah)
        {
            var strWhere ="";
            if(strKind == "RANK")
            {
                strWhere  = "where P.IDRANK ==" + Rank;
            }
            else 
            {
                strWhere  = "where P.IDRANK == " + Rank + " && P.BLAH == " + Blah;
            }

            DBEntities MyDB = new DBEntities();
            var Query1 = from P in MyDB.Per
                            strWhere 
                         select P;
        }

//构建数据表并添加列
DataTable dt=新的DataTable（）；
dt.列添加（“IDRank”）；
dt.列。添加（“废话”）；
//向表中添加行
对于（int i=1；i<5；i++）{
DataRow dr=dt.NewRow（）；
dr[“IDRank”]=i；
dr[“Blah”]=“Blah”+i.ToString（）；
dt.Rows.Add（dr）；
}           
//获取表的数据视图
DataView dv=dt.AsDataView（）；
//定义过滤器
字符串过滤器=“IDRank=2”；
//应用过滤器
dv.RowFilter=过滤器；
//运行查询
var Query1=从dv.ToTable（）中的P开始。AsEnumerable（）选择P；

每个表，我都在编写很多函数。我需要将这些函数转换为一个函数。
例如：每个表有两个函数

private void SelectByRank(int Rank)
        {
            DBEntities MyDB = new DBEntities();
            var Query1 = from P in MyDB.Per
                         where P.IDRANK == Rank
                         select P;
        }
        private void SelectByRankANDBlah(int Rank, string Blah)
        {
            DBEntities MyDB = new DBEntities();
            var Query1 = from P in MyDB.Per
                         where P.IDRANK == Rank && P.BLAH == Blah
                         select P;
        }     

private void Select(string strKind,int Rank, string Blah)
        {
            var strWhere ="";
            if(strKind == "RANK")
            {
                strWhere  = "where P.IDRANK ==" + Rank;
            }
            else 
            {
                strWhere  = "where P.IDRANK == " + Rank + " && P.BLAH == " + Blah;
            }

            DBEntities MyDB = new DBEntities();
            var Query1 = from P in MyDB.Per
                            strWhere 
                         select P;
        }

现在，我将转换为一个函数。例如

private void Select(string strKind,int Rank, string Blah)
        {
            var strWhere ="";
            if(strKind == "RANK")
            {
                strWhere  = "where P.IDRANK ==" + Rank;
            }
            else 
            {
                strWhere  = "where P.IDRANK == " + Rank + " && P.BLAH == " + Blah;
            }

            DBEntities MyDB = new DBEntities();
            var Query1 = from P in MyDB.Per
                            strWhere 
                         select P;
        }

好吗？

我使用这个代码

private void Select(string strKind,int Rank, string Blah)
        {
            var strWhere ="";
            if(strKind == "RANK")
            {
                strWhere  = "where P.IDRANK ==" + Rank;
            }
            else 
            {
                strWhere  = "where P.IDRANK == " + Rank + " && P.BLAH == " + Blah;
            }

            DBEntities MyDB = new DBEntities();
            var Query1 = from P in MyDB.Per
                            strWhere 
                         select P;
        }

using (var context = new DBEntities())
            {
                System.Data.Objects.ObjectQuery<User> contacts = context.Users.Where("it.FirstName = @fname", new System.Data.Objects.ObjectParameter("fname", "Arash"));
                List<User> items = contacts.ToList();
            }

使用（var context=new DBEntities（））
{
System.Data.Objects.ObjectQuery contacts=context.Users.Where（“it.FirstName=@fname”，new System.Data.Objects.ObjectParameter（“fname”，“Arash”）；
列表项=contacts.ToList（）；
}

Use PredicateBuilder：您能解释一下为什么要这样做吗？强类型语法应该是LINQ查询的一个加号。因为我想要所有程序，请选择一个。请提供更多详细信息。