{“输入字符串的格式不正确。”} [关闭]

Question

protected void UpdateCustomer(object sender, GridViewUpdateEventArgs e)
{
    string CustomerID = ((Label)GridView1.Rows[e.RowIndex]
                        .FindControl("lblCustomerID")).Text;
    string Name = ((TextBox)GridView1.Rows[e.RowIndex]
                        .FindControl("txtContactName")).Text;
    string Company = ((TextBox)GridView1.Rows[e.RowIndex]
                        .FindControl("txtCompany")).Text;
    MySqlConnection con = new MySqlConnection();
    string Connection = "Server=localhost;" +
    "DATABASE=northwind2007;" + "username=;" +
    "PASSWORD=;";
    con.ConnectionString = Connection;
    MySqlCommand cmd = new MySqlCommand();
    cmd = new MySqlCommand(cmd.CommandText, con);
    cmd.CommandType = CommandType.Text;
    cmd.CommandText = "update Customers set FirstName=@ContactName," +
     "Company=@CompanyName where ID=@CustomerID;" + "select ID,FirstName,Company from Customers";
    cmd.Parameters.AddWithValue("@CustomerID", MySqlDbType.VarChar).Value = CustomerID;
    cmd.Parameters.AddWithValue("@ContactName", MySqlDbType.VarChar).Value = Name;
    cmd.Parameters.AddWithValue("@CompanyName", MySqlDbType.VarChar).Value = Company;
    GridView1.EditIndex = -1;
    MySqlDataAdapter da = new MySqlDataAdapter(cmd);
    DataTable dt = new DataTable();
    da.Fill(dt);
    GridView1.DataSource = dt;
    GridView1.DataBind();
}

我已经尝试了所有方法，但现在解决了，每次我尝试从我的网格更新记录时都会引发此错误。

Answer 1

不要使用AddWithValue，而是使用Add：

cmd.Parameters.Add("@CustomerID", MySqlDbType.VarChar).Value = CustomerID;

否则MySqlDbType.VarChar 被视为值。

您还应该执行更新命令并且您需要Open 连接：

con.Open();
int updatedRecords = cmd.ExecuteNonQuery();

如果您想在之后填写表格，可以使用DataAdapter：

using(var da = new MySqlDataAdapter("select ID,FirstName,Company from Customers", con))
    da.Fill(dt);

请注意，您应该始终使用using-statement 来确保将释放任何非托管资源并关闭连接（即使出现错误）。例如：

using(var con = new MySqlConnection())
using(var cmd =  new MySqlCommand("UPDATE ...", con))
{
    con.Open();
    cmd.ExecuteNonQuery();
}