如何修复错误“CS1503 C＃Argument 2：无法从'CoffeeShopApp.CoffeeShopDBEntities'转换为'System.Data.Entity.Core.Objects.ObjectContext'" [英] How can fix the error "CS1503 C# Argument 2: cannot convert from 'CoffeeShopApp.CoffeeShopDBEntities' to 'System.Data.Entity.Core.Objects.ObjectContext'"

问题描述

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Data.Entity.Core.Objects;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace CoffeeShopApp
{
    public partial class frmViewProduct : Form
    {
        CoffeeShopDBEntities cse = new CoffeeShopDBEntities();

        public frmViewProduct()
        {
            InitializeComponent();

            dgv.DataSource = cse.tblProducts.ToList();
            dgv.Columns["ProductType"].Visible = false;
            dgv.Columns["tbleProductType"].Visible = false;
            dgv.Columns["tblTransactionItems"].Visible = false;
        }

        private void cboProductType_SelectionChangeCommitted(object sender, EventArgs e)
        {
            ObjectQuery<tblProduct> filteredProducts = new ObjectQuery<tblProduct>(
                "select value product from tblProduct as product where product.ProductType =" + cboProductType.SelectedValue, cse);--->> I got error here with cse

            dgv.DataSource = filteredProducts;
        }
    }
}

推荐答案

尝试以下流程：



通过实体实体SQL ：

Try with below processes:

Through entity Entity SQL:

//Querying with Object Services and Entity SQL
string sqlString = "SELECT VALUE st FROM CoffeeShopDBEntities.tblProduct AS st WHERE st.ProductType == '" + cboProductType.SelectedValue+ "'";

var objctx = (ctx as IObjectContextAdapter).ObjectContext;
		
ObjectQuery<tblproduct> filteredProducts = objctx.CreateQuery<tblproduct>(sqlString);
</tblproduct></tblproduct>

通过 Native SQL ：

Through Native SQL:

using (var ctx = new CoffeeShopDBEntities())
{
	var filteredProducts = ctx.tblProduct.SqlQuery("select value product from tblProduct as product where product.ProductType = '" + cboProductType.SelectedValue + "'").ToList<tblproduct>();
}
</tblproduct>

注意：上面的代码编写为假设实体名称为tblProduct。如果它与EF中的Products不同，则更改它。

Note: Above code written as assuming the entity name as tblProduct. If it is different like "Products" in EF then change it.

请参阅此处的示例 - 在ADO.NET中使用DataGridView进行数据绑定 [ ^ ]。

See the example here - Databinding with DataGridView in ADO.NET[^].

这篇关于如何修复错误“CS1503 C＃Argument 2：无法从'CoffeeShopApp.CoffeeShopDBEntities'转换为'System.Data.Entity.Core.Objects.ObjectContext'"的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！