如何使用WinForm datetimepicker C＃在SQL数据库中搜索

Question

I created a model that connects SQLserver 2014 and VisalStudio2013(.NET 4,5) , Visal C# .In VB I have two forms аnd in SQL one table with records.

In fist Winform I used "textbox" wich type is nvarchar (10) for searching in SQL database.

**But in the second Winform I want to searching in SQL database using "datetimepicker" where the type of colum is date **

What must change in my code for this seach.Becouse give me : Error 7 Operator '==' cannot be applied to operands of type 'System.DateTime?' and 'int

If must white new code ,what should be ?

This is the code from first form for searching

        textKkKod1.Focus();

        loadSearchData();

        int kochani;
        try
        {
            kochani = Convert.ToInt32(this.textKkKod1.Text);
        }
        catch
        {
            MessageBox.Show("Error 404");
            return;
        }
        string kodNaKonduktor = this.textKkKod1.Text;
        var koch = db.Koches.Where(k => k.CODEK == kochani).FirstOrDefault();

        if (koch == null)
            return;

        this.textKkKod1.Text = Convert.ToString(koch.CODEK);
        //this.textKkKochaniData1.Value = Convert.ToDateTime(koch.DATER);
        this.textKkRazpiska1.Text = koch.Razpiska;



    }

    private void loadSearchData()
    {



        int kochani;
        try
        {
            kochani = Convert.ToInt32(this.textKkKod1.Text);
        }
        catch
        {
            MessageBox.Show("Eror 404");
            return;
        }
        kochBindingSource.DataSource = db.Koches.Where(k => k.CODEK == kochani).ToList();

        this.gridKochaniKonduktor1.DataSource = this.kochBindingSource.DataSource;


    }

Answer 1

The error you are getting is saying that you are trying to compare a date to an integer. You cannot compare two objects of different types.

From the code in your question, this is caused by line:

var koch = db.Koches.Where(k => k.CODEK == kochani).FirstOrDefault();

The same error would also appear here:

kochBindingSource.DataSource = db.Koches.Where(k => k.CODEK == kochani).ToList();

We know kochani is an integer, which means CODEK must be a datetime. (Unless I've missed it, you haven't shown us how CODEK is declared/ initialized/ assigned too.)

You need to either convert CODEK to an integer : (I doubt you'll be able to store a date as an integer actually, best to use long )

long codekAsLong = long.Parse(CODEK.ToString("yyyyMMddHHmmss"));

Or convert kochani to a datetime to fix this.

DateTime kochaniAsDT = new DateTime(1970, 1, 1).AddMilliseconds(kochani);
//This assumes kochani represents milliseconds

-I cannot tell you which as I don't know the context in which this code is being used. (I'm struggling with the variable names enough as it is...)