问题
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();
}
}
回答1:
Why not change your SQL to:
INSERT INTO TestplanTeststep
(TeststepId,TestplanId,CreatedAt,ErrorText,ErrorScreenshot,TestState)
VALUES
(@TeststepId, @TestplanId,@CreatedAt,NULL,NULL,@TestState)
or just
INSERT INTO TestplanTeststep
(TeststepId,TestplanId,CreatedAt,TestState)
VALUES
(@TeststepId, @TestplanId,@CreatedAt,@TestState)
...and omit the two parameters?
If it's always NULL, that will have the same effect.
Otherwise, try it in two lines:
var binary1 = insertCMD.Parameters.Add("@ErrorScreenshot", SqlDbType.VarBinary, -1);
binary1.Value = DBNull.Value;
Otherwise, in your original SQL insert statement, you're not defining the parameter type but passing in varbinary, hence the error.
回答2:
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;
来源:https://stackoverflow.com/questions/11411854/implicit-conversion-from-data-type-nvarchar-to-varbinarymax-is-not-allowed