DBNull exception when passing null value in DB-CodePudding

I have this piece of code and I am getting exception for featureValue.IsVisible. I know that I need to verify to not be DbNull.Value or assing a Value if they are. But I don't know how to do this verifications in my context where I have code in Linq

ComboBoxEdit comboBox = new ComboBoxEdit();


var featureValues = 
        from featureValue in this.productsDataSet.FeatureValues
        where (featureValue.FeatureId == feature.FeatureId && featureValue.IsVisible == true) 
        select featureValue.Value;

comboBox.Properties.Items.AddRange(featureValues.ToArray());
comboBox.Properties.AutoComplete = true;
comboBox.Properties.TextEditStyle = TextEditStyles.DisableTextEditor;

return comboBox;

I tried :

 !IsDbNull(featureValue.IsVisible)
 !IsNull(featureValue.IsVisbile)

The name 'IsNull' does not exist in the current context

 featureValue.isVisbile == DBNull.Value

Operator '==' cannot be applied to operands of type 'bool' and 'DBNull'

!featureValue.IsNull(featureValue.IsVisible)

Cannot convert from 'int' to 'bool' I am getting errors for all

CodePudding user response：

You could try the following

var featureValues = 
    from featureValue in this.productsDataSet.FeatureValues
    where (featureValue.FeatureId == feature.FeatureId && featureValue.IsVisible.HasValue && featureValue.IsVisible == true) 
    select featureValue.Value;

CodePudding user response：

Since featureValue.IsVisible have possible DbNull.Value then you have to check for DbNull before moving on using System.Convert class

If your exception is at featureValue.IsVisible then this section of code snippet:

var featureValues = 
        from featureValue in this.productsDataSet.FeatureValues
        where (featureValue.FeatureId == feature.FeatureId && featureValue.IsVisible == true) 
        select featureValue.Value;

would be:

var featureValues = 
        from featureValue in this.productsDataSet.FeatureValues
        where (featureValue.FeatureId == feature.FeatureId && !Convert.IsDBNull(featureValue.IsVisible) && featureValue.IsVisible == true) 
        select featureValue.Value;

Which basically means before evaluate the featureValue.IsVisible == true, it will check if is NOT DbNull. When if it is DBNull, then && operator will cutshort and will not evaluate featureValue.IsVisible == true