Select Value in DropDownList

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C#

I have a master table called master_litigants
i m populating this data into a dropdown list
the table as follows:-
Litigant_id Litigant_type Litignat_value
1 PETITIONER P
2 RESPONDENT R
3 THIRD PARTY T

ddlLitigantType.DataTextField = "Litigants_Type";
ddlLitigantType.DataValueField = "Litigants_value";
ddlLitigantType.DataBind();
I have inserted Value that is(P,R,T) into other table

for updation i read the data from other and want to show in the dropdown list
for that i m using code
1)ddlLitigantType.SelectedValue = dr["Litigant_type"].ToString();
and
2)ddlLitigantType.Items.FindByValue(dr["Litigant_type"].ToString()).Selected = true;
both code showing Error:

Error for 1)st code is:-ddlLitigantType has a SelectedValue which is invalid because it does not exist in the list of items. Parameter name: value(But the ddlLitigant is loaded in the page load only so the value is present)
Error for 2)nd code is:-Object reference not set to an instance of an object.

m i doing it wrong r is there any other way of doing it.
plZ help me