C# Linq 列名作为变量

private void query(string column, string value) {
    using (var db = new myDB()) {
        var s1 = (from c in db.Components
                  where (**column** == **value**)
                  select new {c.id, **column**});
    }
}

var s1 = (from c in db.Components
          where (c.supplier == "abc")
          select new {c.id, c.supplier});

我想这个例子可能很有用。

 void BindGridTypeSafe()
    {
        NorthwindDataContext northwind = new NorthwindDataContext();
        var query = from p in northwind.Products
                    where p.CategoryID == 3 && p.UnitPrice > 3
                    orderby p.SupplierID
                    select p;
        GridView1.DataSource = query;
        GridView1.DataBind();
    }
    void BindGridDynamic()
    {
        NorthwindDataContext northwind = new NorthwindDataContext();
        var query = northwind.Products
                             .Where("CategoryID = 3 AND UnitPrice > 3")
                             .OrderBy("SupplierID");
        GridView1.DataSource = query;
        GridView1.DataBind();
    }

一个不错的方法是使用动态 Linq

http://weblogs.asp.net/scottgu/archive/2008/01/07/dynamic-linq-part-1-using-the-linq-dynamic-query-library.aspx

像这样：

var s1 = (from c in db.Components
    where(column + "=" + value)
    select new {c.id, **column**});

简短的回答是添加库System.Linq.Dynamic作为参考，并执行以下操作：

string columnName = "Supplier";
var s1 = Suppliers
    .Where(String.Format("{0} == '"abc'"", columnName))
    .Select(new {c.id, c.supplier};

下面是动态 Linq 的完整工作示例，其中列名是一个参数：

using System;
using System.Collections.Generic;
using System.Linq;
using System.Linq.Dynamic;
public class Program
{
    public static void Main()
    {
        var lstContacts = new List<Contact>{
            new Contact{Id = 1, Active = true, Name = "Chris"}, 
            new Contact{Id = 2, Active = true, Name = "Scott"}, 
            new Contact{Id = 3, Active = true, Name = "Mark"}, 
            new Contact{Id = 4, Active = false, Name = "Alan"}};
        string columnName = "Active";
        List<Contact> results = lstContacts.Where(String.Format("{0} == true", columnName)).ToList();
        foreach (var item in results)
        {
            Console.WriteLine(item.Id.ToString() + " - " + item.Name.ToString());
        }
    }
}
public class Contact
{
    public int Id
    {
        get;
        set;
    }
    public bool Active
    {
        get;
        set;
    }
    public string Name
    {
        get;
        set;
    }
}

你可以在这里尝试这个.net-fiddle-

我正在复活这个旧线程，因为我今天不得不在 Core 2.2 ASP.NET 解决这个问题。我使用 System.Linq.Dynamic.Core NuGet 包创建了以下扩展方法，如果您需要检查多个给定字符串值是否包含在多个给定列中，该方法效果很好。

public static IQueryable<TEntity> WhereContains<TEntity>(
    this IQueryable<TEntity> query,
    string field,
    string value,
    bool throwExceptionIfNoProperty = false,
    bool throwExceptionIfNoType = false)
    where TEntity : class
{
    PropertyInfo propertyInfo = typeof(TEntity).GetProperty(field);
    if (propertyInfo != null)
    {
        var typeCode = Type.GetTypeCode(propertyInfo.PropertyType);
        switch (typeCode)
        {
            case TypeCode.String:
                return query.Where(String.Format("{0}.Contains(@0)", field), value);
            case TypeCode.Boolean:
                var boolValue = (value != null
                    && (value == "1" || value.ToLower() == "true"))
                    ? true
                    : false;
                return query.Where(String.Format("{0} == @0", field), boolValue);
            case TypeCode.Int16:
            case TypeCode.Int32:
            case TypeCode.Int64:
            case TypeCode.UInt16:
            case TypeCode.UInt32:
            case TypeCode.UInt64:
                return query.Where(String.Format("{0}.ToString().Contains(@0)", field), value);
            // todo: DateTime, float, double, decimals, and other types.
            default:
                if (throwExceptionIfNoType)
                    throw new NotSupportedException(String.Format("Type '{0}' not supported.", typeCode));
                break;
        }
    }
    else
    {
        if (throwExceptionIfNoProperty)
            throw new NotSupportedException(String.Format("Property '{0}' not found.", propertyInfo.Name));
    }
    return query;
}

该代码可与 一起使用。网络斯坦达/.NETCore（使用前面提到的System.Linq.Dynamic.Core包）以及 ASP.NET 4.x（使用System.Linq.Dynamic包）。

有关 WhereContains 扩展方法和完整用例信息的更多信息，请查看我博客上的这篇文章。

只需使用

typeof 来使用列名

public string columnName(string Id, string columnName, string columndata)
        {
            var story = _CidbContext.Stories.Where(m => m.Id.ToString() == Id).FirstOrDefault();
            var property = typeof(Story).GetProperty(columnName);
            if (property != null)
            {
                var convertedValue = Convert.ChangeType(columndata, property.PropertyType);
                property.SetValue(story, convertedValue);
                _CidbContext.SaveChanges();
                return "Data Saved";
            }
            return "No Column found";
        }