Check if decimal value is null

I would like to check if the decimal number is NULL or it has some value, since the value is assigned from database in class object:

public decimal myDecimal{ get; set; }

and then I have

myDecimal = Convert.ToDecimal(rdrSelect[23].ToString());

I am trying:

if (rdrSelect[23] != DBNull.Value)
                        myDecimal = Convert.ToDecimal(rdrSelect[23].ToString());

But I am getting this:

the result of the expression is always 'true' since a value of type 'decimal' is never equal to null

How can I check if that decimal number has some value?


A decimal will always have some default value. If you need to have a nullable type decimal, you can use decimal?. Then you can do myDecimal.HasValue

you can use this code

if (DecimalVariable.Equals(null))  
   //something statements

decimal is a value type in .NET. And value types can't be null. But if you use nullable type for your decimal, then you can check your decimal is null or not. Like myDecimal?

Nullable types are instances of the System.Nullable struct. A nullable type can represent the normal range of values for its underlying value type, plus an additional null value.

if (myDecimal.HasValue)

But I think in your database, if this column contains nullable values, then it shouldn't be type of decimal.

Assuming you are reading from a data row, what you want is:

if ( !rdrSelect.IsNull(23) ) 
   //handle parsing

Decimal is a value type, so if you wish to check whether it has a value other than the value it was initialised with (zero) you can use the condition myDecimal != default(decimal).

Otherwise you should possibly consider the use of a nullable (decimal?) type and the use a condition such as myNullableDecimal.HasValue

If you're pulling this value directly from a SQL Database and the value is null in there, it will actually be the DBNull object rather than null. Either place a check prior to your conversion & use a default value in the event of DBNull, or replace your null check afterwards with a check on rdrSelect[23] for DBNull.

You can also create a handy utility functions to handle values from DB in cases like these. Ex. Below is the function which gives you Nullable Decimal from object type.

    public static decimal? ToNullableDecimal(object val)
        if (val is DBNull ||
            val == null)
            return null;
        if (val is string &&
            ((string)val).Length == 0)
            return null;
        return Convert.ToDecimal(val);

I've ran across this problem recently while trying to retrieve a null decimal from a DataTable object from db and I haven't seen this answer here. I find this easier and shorter:

var value = rdrSelect.Field<decimal?>("ColumnName") ?? 0;

This was useful in my case since i didn't have a nullable decimal in the model, but needed a quick check against one. If the db value happens to be null, it'll just assign the default value.

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