Retrieving single value from datatable how to check NULL

Question

I am trying to compare the value of a row esmcost with psmcost of table wsmtbl but esmcost cost value is null due to which I am getting the following error:

Operator '<>' is not defined for type 'DBNull' and type 'DBNull'

Is there any way to change the null value to zero?

This is the C# code

ds.Tables["wsmtbl"].Rows[0]["esmcost"] <> ds.Tables["wsmtbl"].Rows[0]["psmcost"]

What is "<>"? What are you trying to do in this line of code, do you mean "!="? — IrishChieftain
– IrishChieftain, Commented Jan 22, 2018 at 13:07

IrishChieftain · Accepted Answer · 2018-01-23 14:57:40Z

1

Try the following.

Decimal esmcost;
if (ds.Tables["wsmtbl"].Rows[0]["esmcost"] == DBNull.Value)
    esmcost = 0.00;
else
    esmcost = Convert.ToDecimal(ds.Tables["wsmtbl"].Rows[0]["esmcost"]);

Decimal psmcost;
if (ds.Tables["wsmtbl"].Rows[0]["psmcost"] == DBNull.Value)
    psmcost = 0.00;
else
    psmcost = Convert.ToDecimal(ds.Tables["wsmtbl"].Rows[0]["psmcost"]);

if (esmcost != psmcost)
{
    ...
}

One could use the ternary operator syntax but I chose the above for readability reasons. For example:

Decimal esmcost = ds.Tables["wsmtbl"].Rows[0]["esmcost"]
    == DBNull.Value ? 0.00 : Convert.ToDecimal(ds.Tables["wsmtbl"].Rows[0]["esmcost"]);

edited Jan 23, 2018 at 14:57

answered Jan 23, 2018 at 14:43

IrishChieftain

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Comments

sanatsathyan · Accepted Answer · 2018-01-22 13:44:39Z

0

Try this,

if(ds.Tables["wsmtbl"].Rows[0]["esmcost"] == DBNull.Value)
{
   ds.Tables["wsmtbl"].Rows[0]["esmcost"] = 0;
}

 ds.Tables["wsmtbl"].Rows[0]["esmcost"] != ds.Tables["wsmtbl"].Rows[0]["psmcost"];

edited Jan 22, 2018 at 13:44

answered Jan 22, 2018 at 12:20

sanatsathyan

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1 Comment

nvoigt Over a year ago

You assume 0 and NULL are the same thing... if that were the case, surely the column would have been NOT NULL anyway and we would never have come to this...

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