Implicit conversion from data type nvarchar to varbinary(max) is not allowed

Question

I get this exception when I try to insert a DBNull.Value into a nullable varbinary(max) field:

Implicit conversion from data type nvarchar to varbinary(max) is not allowed. Use the CONVERT function to run this query.

Thats my code:

  insertCMD.Parameters.AddWithValue("@ErrorScreenshot", SqlDbType.VarBinary).Value = DBNull.Value;

I know there exist duplicate questions on SO, but I do NOT use any String like the others do.

What do I wrong?

UPDATE:

using (var insertCMD = new SqlCommand("INSERT INTO TestplanTeststep (TeststepId,TestplanId,CreatedAt,ErrorText,ErrorScreenshot,TestState) VALUES (@TeststepId, @TestplanId,@CreatedAt,@ErrorText,@ErrorScreenshot,@TestState)", con))
{
 var p1 = insertCMD.Parameters.Add("@TeststepId", SqlDbType.Int);
 var p2 = insertCMD.Parameters.Add("@CreatedAt", SqlDbType.DateTime);
 insertCMD.Parameters.AddWithValue("@TestplanId", testplan.Id);
 insertCMD.Parameters.AddWithValue("@ErrorText", (object) DBNull.Value);
 insertCMD.Parameters.AddWithValue("@ErrorScreenshot", (object) DBNull.Value);
 insertCMD.Parameters.AddWithValue("@TestState", (int)Teststep.TeststepTestState.Untested);

       foreach (Teststep step in teststeps)
        {
           p1.Value = step.Id;
           p2.Value = step.CreatedAt;
           insertCMD.ExecuteNonQuery();
        }
     }

Answer 1

I had the same problem while insertion DBNull.Value for a Varbinary(Max) column. After Googling I found a solution that may help you as well:

You need to set size -1 which means Max length for varbinary column when adding your sql parameter:

this.cmd.Parameters.Add("@Photo", SqlDbType.VarBinary, -1).Value = DBNull.Value;

So in your case:

insertCMD.Parameters.Add("@ErrorScreenshot", SqlDbType.VarBinary,-1).Value = DBNull.Value;