带有 ComboBox 和 Column.Contains 的动态 Linq To Sql

Question

我在表单上有一个文本框、组合框、按钮和 DataGridView，用于从 MSSQL 视图 (vCustomer) 搜索和返回客户信息。它工作得很好，但我知道我的代码可以更有效率。组合框中的四个项目代表要搜索的列。

有没有一种简单的方法可以将以下内容转换为动态 LINQ to SQL？我是 C# 新手。我查看了其他一些帖子，但似乎无法正常工作。

public partial class MainForm : Form
{
    public MainForm()
    {
        InitializeComponent();
    }

    private void MainForm_Load(object sender, EventArgs e)
    {
        // columns to filter for
        string[] list = new string[4];
        list[0] = "Name";
        list[1] = "CustomerAccountNo";
        list[2] = "Telephone";
        list[3] = "Postal";

        // bind to combobox
        cboColumn.DataSource = list;
        cboColumn.SelectedIndex = 0;
    }

    private void btnSearch_Click(object sender, EventArgs e)
    {

        try
        {
            Cursor.Current = Cursors.WaitCursor; 
            CustomerSearchDataContext db = new CustomerSearchDataContext();
            IEnumerable<vCustomer> customerQuery = null;
            switch (cboColumn.SelectedIndex)
            {
                case 0:
                    customerQuery = from c in db.vCustomers
                                    where c.Name.Contains(txtSearch.Text)
                                    orderby c.CustomerAccountNo descending
                                    select c;
                    break;
                case 1:
                    customerQuery = from c in db.vCustomers
                                    where c.Name.Contains(txtSearch.Text)
                                    orderby c.CustomerAccountNo descending
                                    select c;
                    break;
                case 2:
                    customerQuery = from c in db.vCustomers
                                    where c.Telephone.Contains(txtSearch.Text)
                                    orderby c.CustomerAccountNo descending
                                    select c;
                    break;
                case 3:
                    customerQuery = from c in db.vCustomers
                                    where c.Postal.Contains(txtSearch.Text)
                                    orderby c.CustomerAccountNo descending
                                    select c;
                    break;
            }
            customerBindingSource.DataSource = customerQuery;
            dataGridView1.DataSource = customerBindingSource;
            dataGridView1.Columns["CustomerId"].Visible = false;
        }
        catch (System.Data.SqlClient.SqlException ex)
        {
            MessageBox.Show("An Error Occured - " + ex.Message,"Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
        finally
        {
            Cursor.Current = Cursors.Default; 
        }
    }
}

Answer 1

使用[System.Linq.Dynamic][1]。

从方法中获取条件并在单个查询中使用它。

    switch (choice)
    {
        case case1:
            condition = string.Format("{0}.Contains({1})", "Column", "Value"
            break;

Answer 2

嘿，罗尼。我尝试了您的建议并重构了我的代码（见下文）。但是，我收到一个错误：No property or field 'smith' exists in type 'vCustomer'。顺便说一句，MessageBox.Show(condition);行返回看起来正确的 Name.Contains(smith)。

我做错了什么？很抱歉成为菜鸟，感谢您的帮助。

想通了...需要用双引号包裹搜索字符串！代码已编辑。

public partial class MainForm : Form
{
    public MainForm()
    {
        InitializeComponent();
    }
    private void MainForm_Load(object sender, EventArgs e)
    {
        // data column to filter against
        string[] list = new string[4];
        list[0] = "Name";
        list[1] = "CustomerAccountNo";
        list[2] = "Telephone";
        list[3] = "Postal";
        cboColumn.DataSource = list;
        cboColumn.SelectedIndex = 0;

        // left, right or middle search
        string[] list2 = new string[3];
        list2[0] = "Contains";
        list2[1] = "StartsWith";
        list2[2] = "EndsWith";
        cboFilterAtt.DataSource = list2;
        cboFilterAtt.SelectedIndex = 0;
    }

    private void btnSearch_Click(object sender, EventArgs e)
    {
        try
        {
            Cursor.Current = Cursors.WaitCursor; 
            CustomerSearchDataContext db = new CustomerSearchDataContext();
            //string condition = string.Format("{0}.{1}({2})", cboColumn.SelectedValue, cboFilterAtt.SelectedValue, txtSearch.Text);
            string condition = string.Format("{0}.{1}({2})", cboColumn.SelectedValue, cboFilterAtt.SelectedValue, "\"" + txtSearch.Text + "\"");
            MessageBox.Show(condition);
            var customerQuery = db.vCustomers.Where(condition).OrderBy("CustomerAccountNo");
            customerBindingSource.DataSource = customerQuery;
            dataGridView1.DataSource = customerBindingSource;
            dataGridView1.Columns["CustomerId"].Visible = false;
        }
        catch (System.Data.SqlClient.SqlException ex)
        {
            MessageBox.Show("An Error Occured - " + ex.Message,"Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
        finally
        {
            Cursor.Current = Cursors.Default; 
        }
    }
}