Assign Null value to the Integer Column in the Dat

问题:

I have a datatable with One ColumnName "CustomerID" with Integer DataType. Dynamically I want to add rows to the DataTable. For that, I had created one DataRow object like:

  DataTable dt = new DataTable();
  DataRow DR = dt.NewRow();
  DR["CustomerID"] = Convert.ToInt32(TextBox1.Text);

But if the TextBox contains empty string, it throws the error. In that case, I want to assign Null value to the CustomerID. How to do this?

回答1:

A null/empty string is in the wrong format; you would need to detect that scenario and compensate:

    DR["CustomerID"] = string.IsNullOrWhiteSpace(text)
        ? DBNull.Value : (object)Convert.ToInt32(text);

回答2:

DR["CustomerID"] = !string.IsNullOrEmpty(TextBox1.Text)
                   ? Convert.ToInt32(TextBox1.Text)
                   : DBNull.Value;

But you should check also that the value is a valid integer:

int value;
if(int.TryParse(TextBox1.Text, out value))
{
    DR["CustomerID"] = value;
}
else
{
    DR["CustomerID"] = DBNull.Value;
}

回答3:

you could do it like that:

DR["CustomerID"] = string.IsNullOrEmpty(TextBox1.Text) ?
    null : Convert.ToInt32(TextBox1.Text);

回答4:

First of all, of course, the field needs to be set as nullable in the DB.

And then, set it to DBNull.Value

回答5:

Int32 Temp = 0;
if !(Int32.TryParse(TextBox1.Text,Temp))
    DR["CustomerID"] = DBNull.Value
else
    DR["CustomerID"] = Temp

回答6:

You need to check first

if (TextBox1.Text.Length > 0)
{
   DR["CustomerID"] = Convert.ToInt32(TextBox1.Text); 
}
else
{
  DR["CustomerID"] = null;  
}

回答7:

You can use DBNull.

DR["CustomerID"] = (TextBox.Text.Length == 0) ? Convert.ToInt32(TextBox1.Text) : DBNull.Value;

回答8:

 if (TextBox1.Text.Trim() == String.Empty)
    {
        DR["CustomerID"] = null;
    }
    else
    {
        DR["CustomerID"] = Convert.ToInt32(TextBox1.Text);
    }

回答9:

DataTable dt = new DataTable();
DataRow DR = dt.NewRow();

if (String.IsNullOrEmpty(TextBox1.Text))
    DR["CustomerID"] = DBNull.Value;
else
    DR["CustomerID"] = Convert.ToInt32(TextBox1.Text);

回答10:

If you declare the Integer variable as int? it is automatically boxed by the C# compiler and you are able to assign null to that variable. For example:

int? custID = null;

I hope that helps

回答11:

When null is not allowed to be inserted into DR["CustomerID"], you could use (int?)null instead like this:

DR["CustomerID"] = string.IsNullOrEmpty(TextBox1.Text) ?
(int?) null : Convert.ToInt32(TextBox1.Text);